U.S. patent number 7,893,253 [Application Number 11/816,049] was granted by the patent office on 2011-02-22 for solid-phase oligosaccharide tagging: a technique for manipulation of immobilized carbohydrates.
This patent grant is currently assigned to Merck Patent GmbH. Invention is credited to Ole Hindsgaul, Malene Ryborg Jorgensen, Anders Lohse, Rita Martins.
United States Patent |
7,893,253 |
Lohse , et al. |
February 22, 2011 |
Solid-phase oligosaccharide tagging: a technique for manipulation
of immobilized carbohydrates
Abstract
The invention relates to methods of manipulating immobilised
carbohydrates by derivatisation. Depending on the nature of the
derivatisation, the carbohydrate may thereby be more easily
detected and/or identified or handled. In particular, the invention
relates to methods of preparing a reactive sugar comprising the
steps of: i) providing a sample comprising a reducing sugar; ii)
providing a solid support covalently attached to a linker
comprising a capture group comprising an --NH2 group, wherein said
linker optionally is attached to said solid support via a spacer;
iii) reacting said reducing sugar with said --NH2 group, thereby
obtaining an immobilised sugar; iv) reacting free --NH2 groups with
a capping agent, wherein the capping agent comprises a reactive
group capable of reacting with an --NH2 group; and v) reducing
C.dbd.N bonds with a reducing agent, thereby obtaining an reactive
sugar of the structure SugarCHn-NH-- linked to a solid support via
a linker and optionally a spacer, wherein n is 1 or 2.
Inventors: |
Lohse; Anders (Copenhagen,
DK), Jorgensen; Malene Ryborg (Copenhagen,
DK), Martins; Rita (Lund, SE), Hindsgaul;
Ole (Valby, DK) |
Assignee: |
Merck Patent GmbH (Darmstadt,
DE)
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Family
ID: |
36178250 |
Appl.
No.: |
11/816,049 |
Filed: |
February 8, 2006 |
PCT
Filed: |
February 08, 2006 |
PCT No.: |
PCT/DK2006/000066 |
371(c)(1),(2),(4) Date: |
May 07, 2008 |
PCT
Pub. No.: |
WO2006/084461 |
PCT
Pub. Date: |
August 17, 2006 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080227092 A1 |
Sep 18, 2008 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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60652247 |
Feb 11, 2005 |
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Foreign Application Priority Data
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Feb 11, 2005 [DK] |
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2005 00209 |
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Current U.S.
Class: |
536/124;
435/6.19; 435/7.1; 435/7.2; 435/5 |
Current CPC
Class: |
G01N
33/6803 (20130101); G01N 33/6842 (20130101); G01N
33/54353 (20130101); Y10T 436/24 (20150115); Y10T
436/145555 (20150115) |
Current International
Class: |
C07H
3/00 (20060101); C12Q 1/68 (20060101); C12Q
1/70 (20060101); G01N 33/53 (20060101) |
Field of
Search: |
;435/5,6,7.1,7.2
;536/124 |
Other References
Nadkarni Varsha D. et al., Directional Immobilization of Herparin
Onto the Nonporous Surface of Poolystyrene Microplates,
Biotechniques, 1997, pp. 382-385, vol. 23, No. 3. cited by
other.
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Primary Examiner: Riley; Jezia
Attorney, Agent or Firm: Millen, White, Zelano, Branigan,
P.C.
Parent Case Text
This application claims the benefit of the filing date of U.S.
Provisional Application Ser. No. 60/652,247 filed Feb. 11, 2005,
which is incorporated by reference herein.
All patent and non-patent references cited herein are hereby
incorporated by reference.
Claims
We claim:
1. A method of preparing a reactive sugar, comprising the steps of
i. Providing a sample comprising a reducing sugar ii. Providing a
solid support (solid) covalently attached to a linker comprising a
capture group comprising an --NH.sub.2 group, wherein said linker
optionally is attached to said solid support via a spacer iii.
Reacting said reducing sugar with said --NH.sub.2 group, thereby
obtaining an immobilised sugar, iv. Reacting free --NH.sub.2 groups
with a capping agent, wherein the capping agent comprises a
reactive group capable of reacting with an --NH.sub.2 group; v.
Reducing C.dbd.N bonds with a reducing agent; and vi. obtaining an
reactive sugar of the structure SugarCH.sub.n--NH-- linked to a
solid support via a linker and optionally a spacer, wherein n is 1
or 2, wherein step iv is performed prior to step v.
2. The method according to claim 1, which further comprises the
step of vii. Reacting the --NH-- group of the reactive sugar with a
derivatising agent comprising an nitrogen-reactive functional group
(X), thereby obtaining a sugar covalently attached to said
agent.
3. The method according to claim 2, wherein said nitrogen-reactive
functional group is an isothiocyanate, an active ester, a
carboxylic acid, a Michael acceptor, an alpha-beta unsaturated
sulfone, an alkylating agent, an aldehyde, a ketone or a
substituted haloaromatic group bearing an electronegative
group.
4. The method according to claim 2, wherein said derivatising agent
is a spectroscopically detectable compound which is derivatized
with a nitrogen-reactive functional group.
5. The method according to claim 2, wherein said derivatizing agent
is a fluorescent compound derivatized with a nitrogen-reactive
functional group.
6. The method according to claim 4, which furthermore comprises the
step of viii. detecting said agent attached to the sugar by
spectrometry.
7. The method according to claim 2, wherein said derivatizing agent
is a mass spectrometry TAG derivatized with a nitrogen-reactive
functional group, wherein the mass spectrometry TAG is capable of
improving the detection and/or structural characterization of a
sugar.
8. The method according to claim 7, wherein the mass spectrometry
TAG is a molecule comprising bromine.
9. The method according to claim 7, wherein the mass spectrometry
TAG is a charged molecule.
10. The method according to claim 7, wherein the mass spectrometry
TAG is an isotope labeled molecule.
11. The method according to claim 7, which furthermore comprises
the step of viii. detecting said mass spectrometry TAG attached to
said sugar by mass spectometry.
12. The method according to claim 2, wherein said derivatizing
agent is a first binding partner capable of specific interaction
with a second binding partner, and wherein said first binding
partner is derivatized with a nitrogen-reactive functional
group.
13. The method according to claim 12, wherein one binding partner
is a protein and the other binding partner is a ligand of said
protein.
14. The method according to claim 12, wherein one binding partner
comprises an epitope and the other binding partner is an antibody
specifically recognising said epitope.
15. The method according to claim 12, wherein one binding partner
is biotin and the other binding partner is an avidin.
16. The method according to claim 12, wherein the second binding
partner is conjugated to a detectable label.
17. The method according to claim 2, wherein the derivatizing agent
is a nucleic acid derivatized with a nitrogen-reactive functional
group or a protected nitrogen reactive functional group.
18. The method according to claim 17, wherein said nucleic acid is
a DNA.
19. The method according to claim 17, which furthermore comprises
the step of viii. detecting said nucleic acid attached to said
sugar.
20. The method according to claim 19, wherein said nucleic acid is
detected by an essentially complementary nucleic acid conjugated to
a detectable label.
21. The method according to claim 19, wherein detection of said
nucleic acid comprises amplification of the nucleic acid.
22. The method according to claim 2, wherein said agent is a
bifunctional reagent of the structure X-tether-Y or
X-tether-Y.sub.p, wherein X is a nitrogen-reactive functional group
and Y is a second reactive functional group and Y.sub.p is a
protected reactive group Y.
23. The method according to claim 22, wherein said second reactive
functional group Y is a thiol, a carboxyl group, an activated
carboxyl group, a disulfide, an activated disulfide, an alkylating
agent, an alkene, an alkyne, an aldehyde, a ketone an azide or a
group Y.sub.p which is a protected derivative of the aforementioned
group Y or a protected amine.
24. The method according to claim 22, which further comprises the
steps of: viii, providing a second derivatizing agent comprising a
functional group (Z) capable of reacting with Y; and ix. reacting
the functional groups Z and Y, thereby covalently attaching the
second derivatizing agent to the sugar via a tether and the first
derivatizing agent.
25. The method according to claim 24, wherein the second
derivatizing agent is a drug, an imaging agent, a peptide, a
polypeptide, a protein, an enzyme, a nucleic acid, a
spectroscopically detectable compound, a mass spectrometry TAG or a
first binding partner capable of specific interaction with a second
binding partner.
26. The method according to claim 22, which further comprises the
steps of: viii. providing a particle which is a microbial organism,
a micelle, a phage, a viral or a nanoparticle, wherein the particle
comprises a functional group (Z) capable of reacting with Y; and
ix. reacting the functional groups Z and Y, thereby covalently
attaching the particle to the sugar via the tether and the
agent.
27. The method according to claim 1, which furthermore comprises
the steps of viii. contacting the sugar with a detection agent
capable of associating with said sugar; and ix. detecting the
detection agent.
28. The method according to claim 27, wherein said detection agent
comprises aryl boronate or heteroarylboronate.
29. The method according to claim 27, wherein the detection agent
is a polypeptide.
30. The method according to claim 29, wherein said polypeptide is a
lectin, a selectin, a toxin, a receptor, an antibody or an
enzyme.
31. The method according to claim 1, wherein the capture group
comprises the structure M-NH.sub.2, wherein M is a heteroatom.
32. The method according to claim 1, wherein the linker is a
non-cleavable linker which is an optionally substituted alkyl, an
optionally substituted aryl, an optionally substituted ether or an
optionally substituted amide.
33. The method according to claim 1, wherein the linker is a
cleavable linker.
34. The method according to claim 33, wherein the cleavable linker
is cleavable by reaction with acid, base, nucleophiles,
electrophiles, oxidation, reduction, free radicals, light, heat or
enzymes.
35. The method according to claim 33, which furthermore comprises
the step of cleaving said cleavable linker thereby releasing the
sugar, wherein this step may be performed subsequent to step v, vi,
vii, viii or ix.
36. The method according to claim 1, wherein the linker is attached
to said solid support via a spacer.
37. The method according to claim 36, wherein the spacer is in the
range of 0 to 1000 atoms long and optionally branched.
38. The method according to claim 1, wherein the solid support is a
polymer, a solid, an insoluble particle or a surface.
39. The method according to claim 1, wherein the solid support is a
sensor.
40. The method according to claim 1, which furthermore comprises
the step of contacting the sugar with one or more glycosidases,
thereby generating a new reducing sugar, provided that the first
sugar is a substrate for said glycosidase(s).
41. The method according to claim 40, which furthermore comprises
the step of immobilizing newly generated reducing sugars on a solid
support.
42. The method according to claim 1, which furthermore comprises
the step of contacting the sugar with at least one enzyme which is
a glycosyltransferase, a sulfatase, a phosphorylase, a
sulfotransferase, a phosphotransferase, a glycosynthase or a
transglycosidase, thereby converting said sugar into a new
structure.
43. The method according to claim 40, comprising detecting newly
generated sugars or structures.
44. The method according to claim 1, wherein the reducing agent is
a borane or borohydride comprising a BH bond or a silane comprising
a SiH bond.
45. The method according to claim 1, which comprises simultaneous
incubation of the sample comprising the reducing sugar, the solid
support and the reducing agent.
46. The method according to claim 1, wherein the capture group
consists of the structure M-NH.sub.2, wherein M is a heteroatom.
Description
FIELD OF INVENTION
The present invention relates to the field of carbohydrate
manipulation. In particular, the invention relates to methods of
manipulating immobilised carbohydrates by derivatisation. Depending
on the nature of the derivatisation, the carbohydrate may thereby
be more easily detected and/or identified or handled. Thus, in one
aspect the invention relates to the field of carbohydrate detection
and identification.
BACKGROUND OF THE INVENTION
Carbohydrates exist in many forms in nature. In animals including
man, examples include free reducing sugars in solution (such as the
monosaccharide glucose in serum), free oligosaccharides in solution
(such as the disaccharide lactose in milk), they can be attached to
peptides or proteins through covalent linkages to a variety of
amino acids (such as asparagine, serine, threonine and others),
covalently attached to lipids such as ceramide (as in gangliosides)
or attached to membrane anchors via phosphatidylinositols. Sugars
are also found attached to many small molecules including some
involved in metabolism, such as glucuronides. In the above
examples, the length of the sugar chains can vary from one to over
100 sugar residues.
In lower organisms, including bacteria and plants, an even wider
array of structures exists. The surface of bacterial cells can be
covered by sugar polymers that are thousands of residues long,
which can act as antigens in the detection of bacteria and as
vaccines. Sugars are an integral part of bacterial cell walls. The
sugars can themselves be antibiotics (such as the aminoglycoside
antibiotics, for example streptomycin), or can be found as
essential components of antibiotics (such as erythromycin and
vancomycin), as enzyme inhibitors (as in Acarbose) or as
anti-cancer agents (such as for example calicheamycin).
One area of particular interest is the structure of the
carbohydrate chains (glycans) found attached to glycoproteins and
glycolipids. The glycosylation pattern of glycoproteins has been
shown to be important for their biological functions, including
their bioavailability, their targeting, and have even been directly
correlated with the metastatic potential of tumor cells. The
glycosylation pattern of human serum transferrin, for example, is
being used as a diagnostic test for a series of genetic diseases
termed Carbohydrate-Deficient Glycosylation Syndromes. Specific
glycolipid sequences have been shown to be involved in neuronal
development and cell surface signalling, in diabetes, and are
accumulated in certain specific metabolic diseases such as
Tay-Sachs, for which they are diagnostic.
The linkages between the sugar residues in the oligosaccharides and
polysaccharides described above can have either the alpha or beta
configurations, and the glycans can be multiply branched. The
diversity of structures possible for glycan chains is therefore
enormous and their structural characterization is therefore
inherently complex. There is therefore a strong interest in methods
for the detection, structural characterization, identification,
quantitation, and chemical/enzymatic manipulation of carbohydrate
and glycan structures, in research, in diagnostics, in monitoring
the glycosylation of recombinant glycoproteins and in the
development of new pharmaceutical agents.
Several methods are in current use for the analysis for
carbohydrate structures, and these have recently been reviewed.
Underivatized oligosaccharides and glycolipids can be analyzed by
NMR-spectroscopy, by mass-spectrometry, and by chromatography. For
the much larger glycoproteins, mass spectrometry provides more
limited information but analysis of their proteolytic digests, i.e.
glycopeptides, has been extensively used. Indirect structural
information about underivatized oligosaccharides can also be
deduced from their abilities to interact with carbohydrate-binding
proteins such as lectins, antibodies or enzymes.
Carbohydrates themselves have no characteristic chromophores, only
N-acetyl groups, so monitoring their separation by optical or
spectroscopic detection is not commonly used. Pulsed amperometric
detection of the polyols has however been an important technique
for detection in chromatography.
The most widely used method for high-sensitivity detection of
carbohydrates has been the labeling of the reducing ends (lactols,
tautomers of hydroxyaldehydes and hydroxyketones) with either
radioactive or fluorescent TAGs. Both chemical and enzymatic
methods have been described that cleave carbohydrates from
glycoproteins and glycolipids, permitting the generation of the
required reducing sugars from glycoproteins, glycolipids and other
glycoconjugates. Most commonly, such reducing sugars are reacted
with amino-containing derivatives of fluorescent molecules under
conditions of reductive amination: i.e., where the initially formed
imines (C.dbd.N) are reduced to amines (CH--NH) to produce a stable
linkage. In most cases, the labeling reactions have been performed
in solution using a large excess of labeling agent. This requires
separation of the excess labeling agent and its by-products prior
to or during analysis. Other TAGs of utility in mass-spectrometry
have been added in the same manner, by either amination or
reductive amination, the detection then being performed by the
mass-spectrometer.
Once the label has been added to permit specific detection, the
carbohydrates described above can subsequently be subjected to
separation and detection/quantification. Additional structural
information can be obtained by exposing the tagged carbohydrates to
enzymes such as glycosidases. If specific glycosidases act on the
tagged carbohydrates, they can cleave one or more sugar residues
resulting in a change in chromatographic or electrophoretic
mobility, as detected by, for example, a fluorescence detector in
HPLC, CE or by a change in their mobility in SDS-PAGE, or a change
in their mass as detected by a change in m/z value in a
mass-spectrometer. Arrays of enzymes have been used to provide a
higher throughput analysis.
Below a short overview of prior art is given:
Gao et al. 2003 reviews suitable techniques for derivatisation of
carbohydrates in solution. In solution carbohydrates may be
derivatised by reductive amination. In general, --NH.sub.2 groups
of amines may react with aldehyde or ketone group of reducing
sugars, thereby producing compounds of --C.dbd.N structure. Such
compounds may further be reduced for example by NaCNBH.sub.3. Gao
et al., 2003 does not disclose manipulation of immobilised
carbohydrates.
U.S. Pat. No. 5,100,778 describes a method for oligosaccharide
sequencing comprising placing an identifying label on the reducing
terminal residue of an oligosaccharide, dividing into a plurality
of separate portions, treating each portion with for example
specific glycosidases, pooling product and analysing the pools
obtained. The document does not describe immobilised
oligosaccharides.
U.S. Pat. No. 4,419,444 describes methods for chemically binding
organic compounds containing carbohydrate residues to a support
bearing reactive --NH.sub.2 groups. The methods involve either the
periodate oxidation of carbohydrate diols to produce reactive
aldehydes by cleaving of C--C bonds in the carbohydrate or
oxidation of --CH.sub.2OH groups to --CHO groups enzymatically.
Both oxidations will result in alteration of the structure of the
carbohydrate. The reactive aldehydes can be immobilised by reaction
with the --NH.sub.2 groups. After immobilisation of the
carbohydrate containing compound a reduction step (for example
using NaBH.sub.4) may be performed to increase stability. The
document describes neither the immobilization of a reducing sugar
through its reducing end nor manipulation of immobilised altered
carbohydrate containing compounds via the reduced amine bond.
Furthermore, the chemical nature of the carbohydrate has been
altered and this alteration may impair further modulations, such as
specific enzymatic cleavage by glycosidases. The document also does
not describe the addition of any chemical reagents to the
immobilised oligosaccharide that result in the addition of
molecular structures to it.
WO92/719974 describes a method of sequencing oligosaccharides. The
method involves immobilising oligosaccharides on a solid support
and subsequent treatment with a variety of glycosidases. Prior to
immoblisation, the oligosaccharide may be linked to a conjugate.
The document does not describe modulation of immobilised
oligosaccharides other than glycosidase treatment.
The above describes the biological importance and complexity of
glycans, and summarizes some benefits of attaching TAGs to reducing
sugars, such as monosaccharides, as well as to the reducing sugar
end of oligosaccharides. To date, such attachment has been
performed in solution using large excesses of tagging agent (and
often additional chemical agents such as reducing agents), and thus
require time consuming and frequently difficult separation
techniques to be applied before either detection or further
manipulation. Such separation techniques invariably result in
losses of material, and dilution, thus considerably complicating
and biasing the analysis. There is therefore a great need for
simple methods that can install a TAG onto a carbohydrate structure
and further manipulate the structure, without the need for complex
and biased methods for separating reaction starting materials,
reagents, by-products and sought after products. We describe herein
such simple methods.
SUMMARY OF THE INVENTION
The present invention relates to methods of covalent attachment of
reducing sugars, (which may be any of the reducing sugars mentioned
herein below in the section "Reducing sugar") to a solid-support
(which may be any of the solid supports described herein below in
the section "Solid support") through reaction with an immobilized
molecule consisting of an optional spacer (i.e. with or without
spacer) and a linker (which can be cleavable) that incorporates a
capture group containing an --NH.sub.2 functionality. The resulting
immobilized sugar has an acyclic form with a C.dbd.N bond, which
may be in equilibrium with it's cyclic glycosylamine tautomer.
Free --NH.sub.2 groups on the solid support after immobilisation
may be capped and the C.dbd.N bond can be reduced. This method is
outlined in FIG. 1 A+B.fwdarw.E. The figure shows an underivatised
pyranose, which however is meant to represent any reducing
sugar.
In a variation, the methods of the invention may comprise reduction
of the immobilized sugar containing a C.dbd.N bond (exemplified by
structure C, FIG. 1) to CH--NH prior to capping free --NH.sub.2
groups, producing a compound of structure C.sub.red (FIG. 1). The
--NH.sub.2 groups in C.sub.red may then be capped at this stage to
produce a compound of the same structure E as that produced by the
sequence C to D to E described above and shown in FIG. 1.
Compounds of the structure E may thus be produced by either the
sequence A+B goes to C goes to D goes to E, or A+B goes to C goes
to C.sub.red goes to E.
It is therefore an object of the present invention to provide
methods of preparing a reactive sugar, said method comprising the
steps of i. Providing a sample comprising a reducing sugar (such as
A in FIG. 1) ii. Providing a solid support (e.g. solid in FIG. 1)
covalently attached to a linker comprising a capture group
comprising an --NH.sub.2 group, wherein said linker optionally is
attached to said solid support via a spacer (such as B in FIG. 1)
iii. Reacting said reducing sugar with said --NH.sub.2 group,
thereby obtaining an immobilised sugar (such as C in FIG. 1), iv.
Reacting free --NH.sub.2 groups with a capping agent, wherein the
capping agent comprises a reactive group capable of reacting with a
--NH.sub.2 group v. Reducing C.dbd.N bonds with a reducing agent
vi. thereby obtaining a reactive sugar containing the structure
SugarCH.sub.n--NH-- linked to a solid support via a linker and
optionally a spacer, wherein n is 1 or 2 (such as compound E of
FIG. 1), wherein steps iv and v may be performed in any order.
In embodiments of the invention wherein step iv is performed prior
to step v, capping --NH.sub.2 groups in step iv will for example
result in compound D of FIG. 1, whereas the reduction performed in
step v will for example result in compound E of FIG. 1;
In embodiments of the invention wherein step v is performed prior
to step iv, then the reduction of the C.dbd.N bond (for example of
compound C of FIG. 1) will for example result in compound C.sub.red
of FIG. 1. The capping of the --NH.sub.2 groups in step iv will for
example produce the compounds of structure E, FIG. 1. It is
comprised within the present invention that the sample comprising
the reducing sugar may be incubated with the solid support and the
reducing agent simultaneously. Thus, reduction of C.dbd.N bonds
(step v) will be performed immediately following reaction of the
reducing sugar with the --NH.sub.2 group of the solid support (step
iii).
In step iii), preferably, the reducing end of said reducing sugar
is reacted with said --NH.sub.2 group. Thus preferably the aldehyde
group or the hemiacetal of the reducing sugar is reacted with the
--NH.sub.2 group.
It is preferred that the methods further comprise the step of vii.
Reacting the --NH-- group of the reactive sugar (for example
compound E of FIG. 1) with a derivatising agent comprising a
nitrogen-reactive functional group (X), thereby obtaining a sugar
covalently attached to said agent. Said sugar covalently attached
to said agent may for example be compound F of FIG. 1 (when the
derivatising agent is a TAG) or compound H of FIG. 1, when the
derivatising agent is a tether linked to functional group.
The term "TAG" in the present context, and in FIG. 1 (vide infra)
is meant to indicate any atom, molecule or entity that can become
covalently attached to another molecule thereby labelling said
another molecule as having undergone the covalent attachment.
DESCRIPTION OF DRAWINGS
FIG. 1 illustrates an example of the method according to the
invention. FIG. 1: A-E illustrates capture and manipulation of a
reducing sugar on a solid support to give a reactive sugar E. FIG.
1: E-G and J illustrates manipulation of a reactive sugar E on a
solid support, and cleavage of a tagged sugar. The methods of the
invention may comprise one or more of the steps illustrated in the
FIG. 1. In the FIG. 1 the reducing sugar is exemplified with a
pyranose, however any reducing sugar may be used with the method.
The figure shows an example where the linker is linked to the solid
support via a spacer, however, the linker may also be directly
linked to the solid support. The solid support is designated
"Solid" in the figure, however it may be any of the solid supports
mentioned herein below.
FIG. 2. Structures 1-10 of the reducing sugars, and mixtures
thereof, used in the examples of the present invention.
FIG. 3. Synthesis of a linker (14) and structure of a spacer
(15).
FIG. 4. Solution-phase synthesis of the TMR-tagged D-galactose
derivative, GalCH.sub.2--N(R)-TMR (21), and description of
nomenclature used for monosaccharide standards.
FIG. 5. Structures 21-28 of synthetic tagged derivatives of the
eight common mammalian monosoaccharides of general structure
SugarCH.sub.2--N(R)-TMR.
FIG. 6. Structures of the four solid supports B.sup.P, B.sup.0,
B.sup.1 and B.sup.2.
FIG. 7. Structures of some capping agents.
FIG. 8. Structures of some nitrogen-reactive tagging agents used,
of general structure TAG-X
FIG. 9. Example of E goes to J (30) using the protected
nitrogen-reactive agent 29 of general structure
X-tether-Y.sub.P.
FIG. 10. Separation by CE of the eight TMR-labelled monosaccharide
standards shown in FIG. 5. The order of elution is GalNAc (27), Xyl
(24), Man (23), Glc (22), GlcNAc (26), Fuc (25), Gal (21), and GlcA
(28). The top trace is an expansion.
FIG. 11. CE of G.sup.P3 (with LacNAc as the reducing sugar tagged
using TRITC, section 4.2.1).
FIG. 12. Electrospray mass-spectrum in the negative ion mode of
G.sup.P5 (with lacto-N-tetraose as the reducing sugar tagged using
4-bromophenylisothiocyanate, section 4.2.2). The inset is an
expansion showing the two peaks corresponding to the major isotopes
of Br.
FIG. 13. CE of G.sup.P6.sub.a (with monosaccharide mixture 6 tagged
using TRITC, section 4.2.3). X denotes unidentified peaks. The
order of elution is GalNAc (27), Man (23) and Fuc (25). The lower
trace is an expansion.
FIG. 14. CE of G.sup.P7.sub.a (with monosaccharide mixture 7 tagged
using TRITC, section 4.2.4). X denotes unidentified peaks. The
order of elution is GalNAc (27), Man (23) and Fuc (25). The lower
trace is an expansion.
FIG. 15. CE of G.sup.P9 (with the oligosaccharide mixture 9 tagged
using FITC, section 4.2.5). The order of elution is G7 to G2 (FIG.
2).
FIG. 16. CE of G.sup.P10 (ribonuclease B oligosaccharides 10 tagged
using FITC, section 4.2.6).
FIG. 17. CE of G.sup.12 (with Gal 2 as the reducing sugar tagged
using TRITC, section 4.3.1).
FIG. 18. CE of G.sup.15 (with LNT 5 as the reducing sugar tagged
using TRITC, section 4.3.2).
FIG. 19. CE of G.sup.18 (with 8 as the reducing sugar mixture
tagged using TRITC, section 4.3.3). The order of elution is LNT
followed by Gal.
FIG. 20. CE of the cleaved products G.sup.05 (A), G.sup.15 (B) and
G.sup.25 (C) after beta-galactosidase digestion of immobilized LNT
(5), section 5.1.1). The TRITC-labelled LNT tetrasaccharide elutes
first near 36 minutes. Loss of galactose yields the trisaccharide
product eluting after 38 minutes.
FIG. 21. CE of the cleaved product before (trace A) and after
(trace B) incubation of F.sup.24 (maltotriose (G3) as the reducing
sugar tagged using TRITC) with glucoamylase, section 5.1.2). A
reference sample of tagged Glc (22, FIG. 5) was added to the sample
prior to recording trace A.
FIG. 22. CE of the cleaved products obtained after
beta-galactosidase treatment of C.sup.25 (bearing LNT and free
NH.sub.2 groups), followed by capture of the released galactose,
reduction and tagging using TRITC, section 5.2. The order of
elution is LNT, the trisaccharide resulting from loss of galactose
and galactose (21).
FIG. 23. CE analysis of the cleaved products derived from C.sup.22
(immobilized galactose) after capping with various agents,
reduction and labelling using TRITC, section 6.1). The capping
agents were A (acetic anhydride), B (benzoic anhydride), C
(trichloroacetic anhydride) and D (dibromoxylene). Tagged galactose
(21) elutes near 17 minutes in all traces.
FIG. 24. CE of the cleaved product obtained from processing
galactose through the sequence C.fwdarw.C.sub.red.fwdarw..fwdarw.G,
section 6.2). The galactose 21 elutes at 17 minutes.
DETAILED DESCRIPTION OF THE INVENTION
Methods of Manipulating a Reducing Sugar
The present invention relates to methods of manipulating a reducing
sugar. An example of the methods of the invention is outlined in
FIG. 1. It should be noted that the methods of the invention do not
necessarily involve all of the steps illustrated in FIG. 1. Thus
the methods may comprise only some of the steps outlined in FIG. 1.
Preferably, the methods will comprise at least the steps
A+B.fwdarw.C, C.fwdarw.D and D.fwdarw.E, or the steps A+B.fwdarw.C,
C.fwdarw.C.sub.red and C.sub.red.fwdarw.E In FIG. 1 the reducing
sugar is exemplified by a pyranose, however any reducing sugar may
be used with the invention, in particular any of the reducing
sugars described herein below in the section "Reducing sugar". The
--OH group dissecting the pyranose ring in FIG. 1 is meant to
indicate that the reducing sugar may bear one or more hydroxyl
groups attached to it.
Each of the steps of the methods of the invention are described
herein below in more detail, wherein capital letters A to J and
C.sub.red refer to FIG. 1
The identity of each of the compounds or intermediates of the
present invention, for example of compounds A, B, C, C.sub.red, D,
E, F, G, H, I or J may be verified by standard techniques known to
the skilled person, such as by NMR.
A. Reducing Sugar
The term "reducing sugar" as used herein covers the classical
definition of sugars that are capable of reducing Cu.sup.2+ to
Cu.sup.+. Whether a sugar is reducing may for example be tested
using Fehlings reagent. In more modern terminology, reducing sugars
are sugars that comprise an aldehyde group or a hemiacetal of the
formula R.sub.2C(OH)OR', wherein R' is not H. Preferably, a
reducing sugar is a carbohydrate structure containing an aldehyde,
which is in equilibrium with the cyclized form called a hemiacetal.
D-glucose is a non-limiting example of such a reducing sugar. The
most abundant cyclic forms contain 5-membered rings, termed
furanoses, and 6-membered rings termed pyranoses. (See rules of
nomenclature).
The term "sugar" as used herein covers monosaccharides,
oligosaccharides, polysaccharides, as well as compounds comprising
monosaccharide, oligosaccharide, or polysaccharide. The terms
"carbohydrate" and "sugar" are herein used interchangeably.
Oligosaccharides and polysaccharides are compounds consisting of
monosaccharides linked glycosidically. In general polysaccharides
comprise at least 10 monosaccharide residues, whereas
oligosaccharides in general comprise in the range of 2 to 10
monosaccharides. Oligosaccharides and polysaccharides may be linear
or branched. A monosaccharide is defined as a polyhydroxy aldehyde
H--(CHOH).sub.n--CHO or polyhydroxyketone
H--(CHOH).sub.n--CO--(CHOH).sub.m--H, wherein m and n are integers.
Preferred monosaccharides comprises in the range of 4 to 9 carbons,
thus preferably for polyhydroxy aldehydes n is an integer in the
range of 3 to 8 and for polyhydroxyketones n+m is an integer in the
range of 3 to 8. Monosaccharides are compounds such as aldoses and
ketoses and a wide variety of derivatives thereof. Derivation
includes those obtained by oxidation, deoxygenation, replacement of
one or more hydroxyl groups by preferably a hydrogen atom, an amino
group or thiol group, as well as alkylation, acylation, sulfation
or phosphorylation of hydroxy groups or amino groups. According to
IUPAC nomenclature, carbohydrates are compounds of the
stoichiometric formula C.sub.n(H.sub.2O).sub.n, such as aldoses and
ketoses as well as substances derived from monosaccharides by
reduction of the carbonyl group (alditols), by oxidation of one or
more terminal groups to carboxylic acids, or by replacement of one
or more hydroxyl group(s) by a hydrogen atom, an amino group, thiol
group or similar groups or derivatives of these compounds.
In a preferred embodiment, the reducing sugar is a naturally
occurring reducing sugar or a reducing sugar, which has been
liberated from a naturally occurring or recombinantly produced
compound comprising a carbohydrate, preferably without having been
subject to furthermore modifications after liberation. In
particular it is preferred that the reducing sugar, is a naturally
occurring reducing sugar or a reducing sugar liberated from a
naturally occurring or recombinantly produced compound, wherein
none of the alcohol groups of said naturally occurring sugar or
said liberated sugar have been enzymatically transformed to an
aldehyde or ketone by oxidation at the level of the
oligosaccharide. It is also preferred that the reducing sugar, is a
naturally occurring reducing sugar or a reducing sugar liberated
from a naturally occurring or recombinantly produced compound,
wherein said naturally occurring sugar or said liberated sugar have
not been subjected to periodate treatment. It is thus generally
preferred that no alcohol group of said naturally occurring sugar
or said liberated sugar have been transformed to an aldehyde or
ketone. In this context recombinantly produced compounds are
compounds produced by a living organism with the aid of recombinant
technologies, for example heterologous glycoproteins.
Reducing sugars may be derived from a variety of sources. For
example the reducing sugar may be obtained from a living organism
or part of a living organism, such as animals or plants or from one
or more specific animal or plant tissues, from organisms such as
prokaryotic or eukaryotic cells, from viruses, from in vitro
cultivated mammalian cells, insect cells, plant cells, fungi,
bacterial cells, yeast, or phages. For example the reducing sugar
may be isolated from extracts of any of the aforementioned cells,
microbial organisms or living organisms. Such extracts may comprise
reducing sugars, such as free carbohydrates. Extracts may also
comprise compounds comprising monosaccharide, oligosaccharide,
polysaccharide or carbohydrate moieties, notably glycoproteins or
glycolipids or small organic molecules to which carbohydrates are
attached, which are generally referred to as glycosides.
Glycoproteins are compounds in which a carbohydrate component is
linked to a peptide, polypeptide or protein component. Thus as used
herein the term glycoprotein also cover proteoglycans and
glycosaminoglycans. Glycolipids are compounds containing one or
more monosaccharide, oligosaccharide, polysaccharide or
carbohydrate moieties bound by a glycosidic linkage to a
hydrophobic moiety such as an acylglycerol, a sphingoid, a ceramide
(N-acylsphingoid) or a prenyl phosphate. Glycosides are meant to
describe small (MWt 100-5000) organic molecule glycosidically
linked to one or more sugars via either O, N or S.
Reducing sugars may also be the products of chemical synthesis, or
chemical/enzymatic synthesis, such as oligosaccharides prepared in
vitro by chemical synthesis in solution or on the solid phase.
These same synthetic oligosaccharides may be further modified by
enzymatic reaction, such as for example by the sulfation,
phosphorylation or glycosylation. Thus the methods described herein
may also be used for manipulation of synthetic or semi-synthetic
oligosaccharides or oligosaccharide libraries.
Preferably, the monosaccharide, oligosaccharide, polysaccharide or
carbohydrate moiety is liberated from the glycoprotein, prior to
performing the methods of the invention. This may be done by
standard methods known to the skilled person. N-linked
monosaccharides, oligosaccharides, polysaccharides or carbohydrates
may be cleaved from glycoproteins by chemical or enzymatic methods.
Enzymatic methods may for example involve use of glycosidases such
as endoglycosidases H and F or N-glycanases such as PNGase-F.
O-linked monosaccharides, oligosaccharides, polysaccharides or
carbohydrates may be cleaved from glycoproteins by chemical
methods, including hydrazinolysis or alkaline .beta.-elimination or
enzymatically using enzymes such as an O-glycosidase. Chemical
methods useful for release of both N-linked and O-linked includes
reactions with strong nucleophiles and/or strong bases such as
hydrazine. Carbohydrates may be cleaved from small organic
molecules using either acidic or basic reactions, or by the action
of glycosidases.
In one embodiment of the invention a predetermined amount of a
reference standard is added to the sample comprising the reducing
sugar. This may facilitate quantification of said reducing sugar
after immobilisation or after immobilisation and release in
embodiments of the invention wherein the linker is cleavable.
The reference standard may be any compound capable of reacting with
--NH.sub.2, for example any compound comprising one of the nitrogen
reactive functional groups described herein below in the section
"E.fwdarw.F. Adding TAGs". Preferably the reference standard is an
aldehyde or a ketone, more preferably a sugar. In another
embodiment of the invention, the same or different reference
standard is added to the solid support prior to contact with the
solution containing the reducing sugar with or without the added
reference standard included in the solution (see herein below in
section "B. Solid support"). Thus two or more reference standards
may be used, one (or more) added to the solid support prior to
contact of the solid support with the solution comprising a
reducing sugar, and one or more added to the solution containing
the reducing sugar.
One or more reference standards may also be added to the solid
support after contact with the reducing sugar, but preferably prior
to capping. Thus for example the reference standard may be added to
compound C or C.sub.red of FIG. 1, preferably after a washing
step.
In embodiments of the invention wherein the solid support is
coupled to a reference standard (see herein below in section "B.
Solid support") it is preferred that different reference standards
are used.
In one embodiment of the invention the methods comprises a step of
pre-treatment of the sample to be used with the method. In
particular, a sample comprising glycosidically-linked sugars such
as a glycoproteins, glycolipids or glycosides may be pretreated
with a scavenger resin prior to reaction with the solid support.
The scavenger resin is preferably a resin comprising a nucleophilic
group capable of reacting with aldehydes and ketones, including
reducing sugars, preferably the scavenger resin comprises an amino
group or a hydrazine. Incubation of the sample with the scavenger
resin will thus remove additional aldehydes, ketones and reducing
sugars. After pre-treatment, such methods will in general further
comprise the step of liberating reducing sugars from said
glycosidically-linked sugars thereby obtaining a sample comprising
reducing sugars. The vast majority of aldehydes and ketone within
said sample will thus be reducing sugars released from
glycosidically-linked sugars. Said reducing sugars may be liberated
by a number of methods, including chemical or enzymatic methods,
such as any of the methods described herein above in this section.
Treatment of the pretreated sample with for example PNGaseF can
cause the release of reducing oligosaccharides into solution for
capture and manipulation according to the methods of the invention.
The oligosaccharides thus released will be essentially free of
contaminating carbonyl compounds. Release of reducing carbohydrates
may also be effected by other enzymes, such as glycosidases, or
using chemical reactions, after scavenging of contaminating
carbonyl compounds as described above.
B. Solid Support
The methods according to the present invention involve
immobilisation of a reducing sugar to a solid support. Solid phase
chemistry offers a number of advantages, such as easy handling,
purification and concentration of immobilised compounds. However,
not all reactions doable in solution can be performed on solid
phases. The attachment to a solid support practically confer
infinite size to each molecular entity.
This has the effect that the molecule reacts much more slowly in a
bimolecular reaction than the same molecule would do in solution.
Some reactions that may be carried out in solution with an
acceptable yield simply will not perform on solid support.
The term "solid support" as used herein covers physical solids as
well as insoluble polymers, insoluble particles, surfaces,
membranes and resins, preferably the solid support is an insoluble
polymer, an insoluble particle, a surface or a resin.
Thus the "solid support" may be an insoluble inorganic matrix (such
as glass), an insoluble polymer (such as a plastic, for example
polystyrene), an insoluble matrix consisting of parts of both
organic and inorganic components (e.g. some hybrid silicates, such
as compounds of the structure R--Si--O--), organic polymers in
common use in solid-phase synthesis (polystyrenes, PEGA resins, PEG
resins, SPOCC resins and hybrids thereof), polyethylene glycol
chains (which can be soluble in certain organic solvents and made
insoluble by the addition of other solvents). The solid may also be
a metal (such as gold), an alloy, or a composite such as for
example indium-tin oxide or mica.
Any of the above listed solid supports may additionally be coated
with agents that have an affinity for carbohydrates, such as but
not limited to aryl boronates or polymers thereof. Such coatings
can increase the concentration of carbohydrate at the surface of
the solid support, enhancing the rate and yield of capture.
Organic polymers used in solid-phase synthesis for example includes
TentaGel (commercially available from Rapp polymere, Tubingen,
Germany), ArgoGel (commercially available from Argonaut
Technologies Inc., San Carlos, Calif.), PEGA (commercially
available from Polymer Laboratories, Amherst, Mass.), POEPOP (Renil
et al., 1996, Tetrahedron Lett., 37: 6185-88; available from
Versamatrix, Copenhagen, Denmark) and SPOCC (Rademann et al, 1999,
J. Am. Chem. Soc., 121: 5459-66; available from Versamatrix,
Copenhagen, Denmark).
In one embodiment of the invention the solid support is a sensor,
such as a surface acoustic wave sensor (such as any of the sensors
described in Samoyolov et al. 2002, J. Molec. Recognit. 15:
197-203) or a surface plasmon resonance sensor (such as any of the
sensors reviewed by Homola et al., 1999, Sensors and Actuators B,
54: 3-15). Such solid supports may be inorganic materials such as
glass, metals such as gold, organic polymeric materials or hybrids
thereof and may be covered various coatings such as proteins or
polysaccharides, oligomers such as dendrimers or polymers such as
polyacrylamide or polyethylene glycol. In a preferred embodiment
the solid support is glass or PEGA resins.
In one embodiment of the present invention the solid support is
coupled to a reference standard, which may facilitate
quantification of immobilised reducing sugar. In particular, it is
preferred that said reference standard is attached to the solid
support (either directly or indirectly) by a cleavable linker,
which could facilitate quantification of immobilised and released
reducing sugar. In embodiments of the invention wherein the
reducing sugar is immobilised to the solid support via a cleavable
linker, it is preferred that the reference standard is immobilised
to the solid support via an identical or similar cleavable
linker.
The reference standard may be any detectable compound, for example
the reference standard may or may not be a sugar, preferably
however it is carbohydrate.
The amount of reference standard may vary, in general the solid
support may comprise in the range of 20 to 500, preferably in the
range of 50 to 200, such as in the range of 90 to 110-NH.sub.2
groups per reference standard.
B. Spacer
According to the present invention the solid support is optionally
coupled to a linker via a spacer. However, it is also comprised
within the present invention that the solid support is directly
coupled to the linker.
A spacer is a chemical entity in the range of 1 to 1000 atoms long.
Preferably, said spacer is a linear or branched chain and/or a ring
structure. The nature of the spacer may be hydrophobic or
hydrophilic or have a mixture of these two properties. The group of
spacers comprises molecules in common use in solid phase synthesis
and on-bead, in-well or on-slide assays involving the detection of
molecules attached via spacers to solid-supports. The skilled
person will readily be able to identify a useful spacer for a given
solid support.
The spacer is preferably an alkyl chain (more preferably a C.sub.1
to C.sub.1000 alkyl chain), which optionally may be branched,
wherein said alkyl chain optionally is substituted at one or more
positions by groups containing one or more of B, O, N, S, P, Si, F,
Cl, Br or I. The spacer may also comprise one or more aryl residues
which optionally may be branched or substituted in the same manner.
In one preferred embodiment, the spacer is selected from the group
consisting of amides and ethers. Thus the spacer may essentially
consist of a chain containing one or more amide bonds (--CONH--),
one more ethylene glycol units (--CH.sub.2--CH.sub.2--O--), or
combinations of these units with the alkyl or aryl chains.
In one embodiment of the invention, the spacer preferably does not
comprise either a primary or a secondary amine. In another
embodiment of the invention any amines comprised within the spacer
are capped.
B. Linker
The present invention relates to capture of reducing sugars onto
solid supports covalently attached to a linker comprising a capture
group. The linker serves to link the capture group, terminating in
--NH.sub.2, to the solid support optionally through a spacer. The
linker may be any of a large variety of linkers such as those in
common use in solid-phase organic synthesis.
The linker may either be a non-cleavable linker or a cleavable
linker.
Non-cleavable linkers may for example be alkyl, aryl, ethers or
amides, wherein any of the aforementioned may optionally be
substituted. For example any of the aforementioned may be
substituted with heteroatoms or they may contain, O-alkyl, alkyl,
aryl or heteroatoms as branches. In one example the linker
comprises or essentially consists of PEG and/or polyamide.
The linker may comprise a site where a reaction can be made to
occur to sever the part containing the capture group (including the
molecules it has captured and which have been optionally further
modified) from the spacer and the solid support. Such linkers are
referred to as cleavable linkers, and are in wide use in solid
phase organic synthesis. Examples of cleavable linkers are known
where the cleavage can be effected by electrophiles, nucleophiles,
oxidizing agents, reducing agents, free radicals, acid, base,
light, heat or enzymes.
Cleavable linkers may for example be acid labile (for example, the
Rink amide as described in Rink, 1987, Tetrahedrom Lett., 28: 387
and traceless silyl linkers as described in Plunkett et al., 1995,
J. Org. Chem., 60: 6006-7), base labile (for example, HMBA as
described in Atherton et al. 1981, J. Chem. Soc. Perkin Trans, 1:
538), or photolabile (for example, 2-nitrobenzyl type as described
in Homles et al., 1995, J. Org. Chem., 60: 2318-2319). The linkers
may be more specific and restrictive of the type of chemistry
performed, such as silyl linkers (for example, those cleaved with
fluoride as described in Boehm et al., 1996, J. Org. Chem., 62:
6498-99), allyl linkers (for example, Kunz et al., 1988, Angew.
Chem. Int. Ed. Engl., 27: 711-713), and the safety catch
sulfonamide linker (for example, as described in Kenner et al.,
1971, Chem. Commun., 12: 636-7). Enzyme cleavable linkers may for
example be any of the enzyme cleavable linkers described in Reents
et al., 2002, Drug Discov. Today, 7: 71-76, or any functionalised
derivatives of the enzyme-labile protecting groups described in the
review by Waldmann et al., 2001, Chem. Rev. 101: 3367-3396. Heat
labile linkers may for example be of the type described in Meng et
al., 2004, Angew. Chem. Int. Ed., 43: 1255-1260.
B. Capture Group
According to the present invention the linker comprises a capture
group, wherein the capture group comprises at least one --NH.sub.2
group. In a favourable format, the capture group terminates in an
--NH.sub.2 group that is attached to the linker through an optional
group R. Thus the capture group preferably is of the structure
R--NH.sub.2. R may be a simple alkyl, aryl or substituted alkyl or
aryl group. Preferably, R should contain a heteroatom directly
attached to the --NH.sub.2 group, to produce structures of the type
linker-M-NH.sub.2, wherein M is a heteroatom (i.e. not carbon),
preferably M is selected from the group consisting of N, O and S.
Especially favourable are compounds where M is a heteroatom, such
as in the structures linker-O--NH.sub.2, linker-NH--NH.sub.2,
linker-CO--NH--NH.sub.2, linker-NH--CO--NH--NH.sub.2,
linker-S(O).sub.2NH--NH.sub.2 and linker-S--NH.sub.2.
A+B.fwdarw.C. Methods of Capture
The capture of the reducing sugar is done by reacting the
--NH.sub.2 group of the capture group with the reducing end of said
reducing sugar, i.e. with the aldehyde or hemiacetal group. The
reaction can occur at any pH values but is most favored in the
range of pH 2-9. The methods may involve the addition of one or
more additives, such as additives which may either facilitate or
favourably alter the equilibrium between the open chain aldehyde
form of the reducing sugar and the hemiacetal form of the reducing
sugar (e.g. compound A, FIG. 1), wherein the open chain aldehyde
form is preferred. The additive may for example be metal ions,
boronates or silicates. The capture produces a species attached to
the solid support through a covalent double bond (shown as C.dbd.N)
where the C is derived from the sugar moiety and N from the capture
group. This immobilized sugar may also be in equilibrium with its
cyclic ring form, in particular if the reducing sugar was a
pyranose, then the immobilised sugar may be in equilibrium with its
cyclic 6-membered ring form (see for example compounds C and C' of
FIG. 1), but it may also be in equilibrium with its 5-membered ring
form if the appropriate OH group on the sugar is unsubstituted.
The capture reaction may be performed in any useful solvent. A
person of ordinary skill in the art will readily be able to
identify a useful solvent for any given compounds A and B. The
solvent may for example be selected from the group consisting of
water, aqueous buffer, organic solvents and mixed aqueous and
organic solvents. The solvent may also be any of the aforementioned
comprising one or more additives such as acids, bases, salts,
divalent metal cations, detergents, complexing agents including
inclusion-complex-forming molecules such as cyclodextrins or
calixarenes, chelating agents (for example EDTA), borates,
boronates or silicates.
In a preferred embodiment the amount of solid support (compound B
of FIG. 1) added to the reaction is adjusted so that a molar excess
of capture groups are present in relation to the reducing sugar,
preferably said excess is large, such as at least 2 times,
preferably at least 5 times, more preferably at least 10 times,
such as at least 50 times, for example at least 100 times or more.
This excess will ensure a more efficient capture of the reducing
sugar.
The capture reaction may be carried out at any temperature, but
preferably at temperatures in the range of 0 to 100.degree. C.
C. Washing
Once the reducing sugar has been immobilised on the solid support
through reaction with the capture group (step A+B.fwdarw.C of FIG.
1) the solid supports may be washed to remove non-covalently bound
material. Accordingly, if the reducing sugar is provided in a
solution comprising other compounds, in particular other compounds
that do not comprise --NH.sub.2 reactive groups, the reducing sugar
may be purified from said solution. It is thus comprised within the
present invention that the reducing sugar is provided in a
non-purified form, such as in the form of a crude cellular extract
or the like. It is also comprised that the reducing sugar may be
produced from a purified or partially purified glycoprotein,
glycolipid or glycoside by the action of an enzymes such as
glycosidase or an amidase or through the cleavage of a glycosidic
bond by chemical reagents.
The skilled person will readily be able to identify suitable
washing conditions for a given immobilised sugar (compound C, FIG.
1). The washing may for example be done with any of the
above-mentioned solvents optionally comprising any of the
above-mentioned additives in addition to detergents and denaturing
agents. The washing my be performed at any temperature, but
preferably at temperatures in the range of 0-100.degree. C.
C.fwdarw.D. Capping
The solid support coupled to the immobilised sugar (such as
compound C of FIG. 1) still contains unreacted free --NH.sub.2
groups and can be subjected to unique manipulations that increase
the scope of its utility.
In one preferred embodiment of the invention, subsequent to
immobilisation of the reducing sugar, unreacted --NH.sub.2 groups
are capped by a capping agent, such as an acylating agents (e.g.
acetic anhydride) or other nitrogen-reactive agents well known in
the art, under conditions where the C.dbd.N bond of C does not
react. After capping the solid support will no longer comprise any
free amine groups, but only capped nitrogen atoms (N(H)CAP) of very
low reactivity towards electrophiles. The product of the capping of
compound C has for example the general structure D (see FIG. 1)
containing an --R--N(H)CAP group, wherein the (H) may or may not be
present depending on the structure of the CAP group.
Thus if the C.dbd.N bond linking the sugar to the solid support is
reduced to an --NH--, it will be a formally SP.sup.3-hybridized
nitrogen atom in the sequence R--NH--CH.sub.2--. Specific reactions
may thus be directed to this group allowing specific and
stoichimetric reactions at the reducing sugar.
Preferably the capping agent specifically reacts with the remaining
--NH.sub.2 groups, without substantially reacting with the C.dbd.N
functionality. Such reagents are well known in the art an include
common acylating agents used for amid bond formation, e.g. acetic
anhydride, other alkanoic acid anhydrides, aromatic anhydrides
(e.g. benzoic anhydride), cyclic anhydrides (e.g. succinic
anhydride, phthalic anhydride), other active esters such as
N-hydroxysuccinimide esters, pentafluorophenyl esters and a variety
of active esters in common use in amide bond formation including in
the solid phase synthesis of peptide bonds. The --NH.sub.2 groups
may alternatively be capped by adding the corresponding free acids
and an in-situ activating agent such as DCC, in common use in
peptide-bond formation thereby creating an active ester in situ.
Other reagents known to be reactive towards --NH.sub.2 groups can
be used, such as alkyl isothiocyanates (R--NCS), aryl
isothiocyantes (Ar--NCS), alkylating agents R-L (where L is a
leaving group typically from the series Cl, Br, I, OS(O).sub.2R'
where R'can be alkyl or aryl), Michael acceptors such as alpha-beta
unsaturated carbonyl compounds (CHR.dbd.CH--CO-- where R can be H,
alkyl or aryl or substituted alkyl or aryl) or alpha-beta
unsaturated sulfones (CHR.dbd.CHS(O).sub.2R' or Ar where R can be
H, alkyl or aryl or substituted alkyl or aryl), sulfonating agents
(such as RSO.sub.2Cl) and derivatives thereof. In a similar manner,
the --NH.sub.2 groups can be capped by reaction with active esters
of carbonates of the general formula RO--C(O) L, where L is
described as above.
D.fwdarw.E. Reduction
In a preferred embodiment of the invention, the C.dbd.N bond
linking the sugar to the linker (for example compound D of FIG. 1)
is reduced using a reducing agent. The C.dbd.N bond may be reduced
by a variety of well known reducing agents, preferably the reducing
agent is capable of saturating the double bond while placing a
hydrogen atom on the N.
Of special value are boranes or borohydrides comprising a BH bond,
examples include NaBH.sub.4, NaCNBH.sub.3, and BH.sub.3 complexes
such as BH.sub.3-pyridine, BH.sub.3-dimethylsulfide or the like.
Silanes with the structures R.sub.3SiH can also be used, such as
silanes comprising SiH bonds, as can hydrogen transfer agents such
as diimides, or homogeneous hydrogenation catalysts or
hydrogenation catalysts comprising a metal-H bond.
The reduction results in a reactive sugar containing the structure
SugarCH--NH-- preferably linked to a solid support via a linker and
optionally a spacer. In general, if the reducing sugar was an
aldehyde, then reduction will result in a compound of the structure
SugarCH.sub.2--NH--. If the reducing sugar was a ketone, then the
reduction will result in a compound of the structure
SugarCH--NH--.
The products of the reduction are for example of the general
structure E (FIG. 1) containing a formally SP.sup.3 hybridized N
atom.
C.fwdarw.C.sub.red.fwdarw.E
In another preferred implementation of the method, the order of the
capping and reduction steps is reversed. Reduction of the C.dbd.N
bond in compound C (FIG. 1) can be effected by any of the reagents
described in D.fwdarw.E above to produce a compound of the
structure C.sub.red (FIG. 1). The reduction may also be performed
in situ, meaning that a reducing agent (such as NaCNBH.sub.3) may
be added to the solid support (e.g. compound B) simultaneously with
the reducing sugar so that the C.dbd.N bond is reduced as it forms
producing also C.sub.red. It is thus comprised within the present
invention that the sample comprising the reducing sugar may be
incubated with the solid support and the reducing agent
simultaneously. Thus, reduction of C.dbd.N bonds (step v) will be
performed immediately following reaction of the reducing sugar with
the --NH.sub.2 group of the solid support (step iii). The free
--NH.sub.2 groups in C.sub.red may then be capped using any of the
reagents described in C.fwdarw.D above under conditions that do not
cause reaction with the SugarCH--NH-moiety. In particular, in this
embodiment of the invention it is preferred that the capping agent
preferentially reacts with primary amino groups over secondary
amino group. It is also preferred that reaction temperature and
time are adjusted to yield preferential reaction with primary over
secondary amino groups. Virtually all compounds that react with
amino groups react more quickly with primary amino groups than with
more substituted amino groups, but this is especially the case when
such compounds are sterically large, such as for example active
benzoyl esters, isopropanoic acid active-esters, pivaloyl
active-esters, Boc anhydride or Boc-azide and the like. Useful
compounds and conditions for preferential reaction with primary
amino groups over secondary amino groups are described in Greene et
al. 1999, Protective Groups in Organic Synthesis, 3.sup.rd. Ed.,
Chaper 7, pp. 503-653. Other very preferred capping agents are
NHS-esters or sterically hindered pentafluorophenyl (PFP) esters or
tetrafluorophenyl (TFP) esters.
E.fwdarw.F. Adding TAGs
Compound E, FIG. 1, obtained by either of the above routes,
contains solids linked to a capped nitrogen atom (N(H)CAP) of very
low reactivity towards electrophiles and a formally
SP.sup.3-hybridized nitrogen atom in the sequence
SugarCH.sub.2--NH--R. Reaction of E with suitable nitrogen-reactive
functional groups (preferably the nitrogen-reactive functional
group is a mild electrophile) therefore results in the exclusive,
or near exclusive, addition of the electrophile to the SP.sup.3
nitrogen atom effectively adding a molecular structure, herein
described as "TAG", or another derivatising agent onto the nitrogen
to which the sugar is attached. The product of the addition of a
TAG is shown as F in FIG. 1.
Throughout the description the term "nitrogen-reactive group" is
used to describe reactivity towards a formally SP.sup.3-hybridized
nitrogen, such as in compounds of the structure R--NH--R', for
example amines, wherein R and R' independently are alkyl, or aryl
(optionally substituted) or compounds wherein R' has an heteroatom
such as O or N attached to the --NH-- such as in hydroxylamine
derivatives (R--NH--OR') or hydrazine derivatives
(R--NH--NH--R').
The identity of the derivatising agent (for example a TAG), i.e.
the specific chemical structure of the derivatising agent, may be
selected by the user. For addition to the SP.sup.3 nitrogen in E,
the derivatising agent (for example the TAG) should itself comprise
an nitrogen-reactive functional group designated "X" in FIG. 1,
Preferably the TAG should contain an electrophile, or be attached
to an nitrogen-reactive functional group X. Preferably the
derivatising agent is of the general structure TAG-X (see FIG. 1),
wherein X is a nitrogen-reactive functional group. Preferably X is
any mild electrophile that is reactive with SP.sup.3 nitrogen
atoms, but preferably mild electrophiles that react poorly with the
--OH groups present on the sugar. Such mild electrophiles include
isothiocyanates (TAG-NCS), active esters (TAG-C(O)-L) where L is a
leaving group commonly used in amide bond formation such as in the
synthesis of peptide bonds, carboxylic acids (TAG-COOH) which can
be activated to active esters in situ by methods commonly used in
amide bond formation such as in the synthesis of peptide bonds,
alkylating agents (TAG-L) where L is a leaving group preferably but
not exclusively from the series Cl, Br, I, OS(O).sub.2R where R can
be alkyl or aryl, TAGs comprising Michael acceptors (typically
containing the sequence --CR.dbd.CH--C(O)--) or alpha-beta
unsaturated sulfones (--CR.dbd.CH--S(O).sub.2--) and derivatives of
any of the aformentionned, aldehydes or ketone that may react with
the sugarCH.sub.2--NH-amino group by reductive amination, or
substituted haloaromatic groups where the aromatic ring bears
electronegative groups such as nitro groups, for example as in the
Sanger reagent 1-fluoro-2,4-dinitrobenzene or the
4-halo-7-nitro-2-oxa-1,3-diazole (NBD) reagents where the halogens
preferably F or Cl.
The TAG may for example be a fluorescent moiety, a mass
spectrometry TAG, a first binding partner capable of binding to a
second binding partner, a nucleic acid wherein any of the
aforementioned TAGs preferably comprises or are attached to an
nitrogen-reactive functional group. In particular the TAG may be
any of the TAGs described in more detail herein below, wherein any
of these TAGs may be attached to any of the aforementioned
nitrogen-reactive functional groups.
An example of a compound which may be obtained by adding a TAG to
compound E is shown as F in FIG. 1.
F. Washing
In one embodiment the tagged sugar (e.g. compound F, FIG. 1) is
washed prior to any further manipulations. Thus any amount of
unbound TAG is removed. Washing may easily be accomplished because
the tagged sugar is immobilised on a solid support.
After washing, only covalent bound TAG will be present. Thus the
amount of TAG will be correlatable to the amount of immobilised
sugar. Accordingly, by determining the presence of TAG, the amount
of immobilised sugar may be determined. If essentially all reducing
sugar in a given sample was immobilised, the methods therefore in
one aspect allow determining the amount of reducing sugar present
in a sample.
The skilled person will readily be able to identify suitable
washing conditions for a given tagged, immobilised sugar (e.g.
compound F, FIG. 1). The washing may for example be done with a
solvent selected from the group consisting of water, aqueous
buffer, organic solvents and mixed aqueous and organic solvents.
The solvent may also be any of the aforementioned comprising one or
more additives such as salts, divalent metal cations, detergents,
complexing agents including inclusion-complex-forming molecules
such as cyclodextrins or calixarenes, chelating agents (for example
EDTA), borates, boronates or silicates. Furthermore, the solvent
may optionally comprise detergents and denaturing agents. The
washing my be performed at any temperature, but preferably at
temperatures in the range of 0-100.degree. C.
H. Cleavage of Cleavable Linker
When the linker used is a cleavable linker, then methods of the
invention may comprise a step of cleaving said cleavable linker
thereby releasing captured sugar. Preferably the cleavage is
performed subsequent to addition of a derivatising agent, such as a
TAG (added using TAG-X) or a tether-Y (added using X-tether-Y) to
the --NH-- group of the immobilised sugar. Thus a tagged sugar
(compound G or compound J in FIG. 1) may be released into solution
from F or from 1, respectively. G consists of a sugar portion that
bears a TAG on the Nitrogen atom which is attached to the residue
(if any) of the linker that remains after cleavage, and for
simplicity is denoted as sugar-TAG. J consists of a sugar portion
that bears a tether on the nitrogen atom, which is attached to the
residue (if any) that remains after cleavage. The tether may
optionally be linked to a TAG.
However, the cleavable linker may be cleaved at any desirable time
within the method.
If the TAG added to compound E has beneficial spectroscopic
properties such as fluorescent properties, the amount of sugar-TAG
(compound G, FIG. 1) can be quantitated in solution. Furthermore,
the sugar-TAG (compound G, FIG. 1) can be subjected to analytical
separation techniques such as HPLC or CE, and if more than one
sugar is present, the individual components can be separated, their
relative ratios determined, and they can be identified if authentic
standards are available, and they can be quantitated. They can also
be used as ligands that may bind to carbohydrate-recognizing
proteins, thus providing information on the structure of either the
carbohydrate or the protein.
If the TAG is a structure giving the sugar-TAG properties that are
beneficial to the practice of mass-spectrometry, either due to
increased sensitivity, simplification of spectral interpretation,
or permitting the performance of differential analysis using
isotope encoding, then the sugar-TAG released into solution can be
favourably analyzed by mass-spectrometry.
F. TAGs with Spectroscopic Properties
In one preferred embodiment of the invention the TAG added to e.g.
compound E or compound H has beneficial spectroscopic properties.
Preferably, the TAG with the beneficial spectroscopic properties is
added to e.g. compound E using a derivative of the structure X-TAG,
wherein X is a nitrogen reactive functional group, such as any of
the nitrogen reactive functional groups described herein above in
the section "E.fwdarw.F Adding TAGs". By beneficial spectroscopic
properties is meant that the TAG can easily be visualised, for
example by spectrometry. Thus the TAG may for example be
spectroscopically detectable. In a preferred embodiment the TAG is
a fluorescent TAG. Examples of such tagging include the reaction
with isothiocyanates (e.g. FITC, TRITC), active esters, Michael
acceptors, alpha-beta-unsaturated sulfonyls (specifically vinyl
sulfones) and alkylating agents such as alkyl halides and
tosylates, an halo-aryl compounds such as for example the Sanger
reagent
The product of addition of such a TAG (for example compound F of
FIG. 1) can absorb and re-emit light that can be detected. The
number of such TAGs present on F will reflect the number of sugar
molecules A added to B and captured to produce C. The number of
reducing sugar molecules (A) originally present in a sample can
therefore be estimated by the fluorescence of compound F, provided
that the provided solid supports (compound B) comprise an excess of
capture groups. TAGs other than fluorescent molecules can also be
used. These can include radioactive TAGs, phosphorescent TAGs,
chemiluminescent TAGs, UV-absorbing TAGs, nanoparticles, quantum
dots, coloured compounds, electrochemically-active TAGs,
infrared-active TAGs, TAGs active in Raman spectroscopy or Raman
scattering, TAGs detectable by atomic force microscopy or TAGs
comprising metal atoms or clusters thereof.
If the solid support of compound F is a sensor, such as a surface
acoustic wave sensor or a surface plasmon resonance sensor, then
addition of such a species that binds specifically to the TAG can
result in the production of a signal that is proportional to the
TAG and therefore to the number of sugar molecules. An example is
when the TAG is a biotin residue, commonly introduced by reaction
with an active ester of biotin. Addition of an avidin-protein to
compound E, when the TAG is a biotin residue, can result in signal
that is readily detected and reported by the sensor. Other examples
of sensors that can be used to detect the binding of second binding
partners to immobilized TAGs include but are not limited to
piezoelectric sensors, amperometric sensors, surface plasmon
fluorescence spectroscopy sensors, dual polarization interferometry
(DPI) sensors, wavelength-interrogated optical sensors (WIOSs),
impedence sensors, optical waveguide grating coupler sensors,
acoustic sensors and calorimetric sensors.
Once the sugar has been attached to a TAG with spectroscopic
properties, then said spectroscopic properties may be determined.
The optical properties may be determined for sugars still
immobilised on the solid support (such as for compound F or I of
FIG. 1) or for sugars released to solution (for example for
compound G or J of FIG. 1). The latter requires that the linker is
a cleavable linker. Depending on the nature of the TAG with
spectroscopic properties, said properties may be determined using
conventional methods, such as spectrometry. Thus the methods of the
invention may comprise the step of detecting the TAG attached to
the sugar by spectrometry.
F. Mass-Spectrometry Tags
In one embodiment of the invention, the TAG is a mass spectrometry
TAG. Said mass spectrometry TAG is preferably added by a reagent of
structure X-TAG, wherein X is a nitrogen-reactive functional group,
such as any of the nitrogen-reactive functional group mentioned
herein above in the section "Adding TAGs". The term "mass
spectrometry TAGs" as used herein refers to molecules that improve
the detection and structural characterization of the products by
mass spectrometry, preferably after cleavage from the solid support
(as described herein above in the section "Cleavage of cleavable
linker"). Examples include the introduction of a bromine label
which imparts a characteristic isotope pattern in the
mass-spectrum. Such a bromine label may be added, for example, by
addition of p-bromophenyl isothiocyanate to compound E producing a
compound of structure F where the TAG contains a bromine atom. The
usefulness of bromine-containing labels in the mass-spectrometry of
carbohydrates has been described for example in Li et al., 2003,
Rapid. Commun. Mass Spectr., 17: 1462-1466. Another example
includes introduction of molecules that impart either positive
charges or negative charges for enhanced detection in either
positive-ion mode or negative-ion mode of mass/charge separation.
Another example includes the introduction of molecules that improve
performance or sensitivity in electrospray, MALDI or other
techniques of ionization common in the practice of mass
spectrometry. Yet another example includes the introduction of
stable isotope-labeled molecules that allow quantitation of the
labelled species by mass-spectrometry. Useful methods for isotope
labelling are for example reviewed in Tao et al., 2003, Current
Opinion in Biotechnology, 14: 110-118.
Once the sugar has been attached to a mass spectrometry TAG, then
the tagged sugar (F or G or I or J, FIG. 1) may be detected by mass
spectrometry. Mass spectrometry may be performed on sugars still
immobilised on the solid support (such as for compounds F and I of
FIG. 1), but preferably is performed on sugars released to
solution, for example by cleavage of a cleavable linker (for
example for compounds G or J of FIG. 1). It is thus preferred that
the linker is a cleavable linker. The skilled person will be able
to perform a suitable mass spectrometry depending on the nature of
the mass spectrometry TAG. Thus the methods of the invention may
comprise the step of detecting the sugar attached to the mass
spectrometry TAG by mass spectrometry.
F. Binding Partner TAGs
In another preferred embodiment of the present invention the TAG is
a first binding partner, capable of specific interaction with a
second binding partner, wherein said first binding partner is added
to for example compound E (or to compound H) through the reaction
with a reagent of structure X-TAG, wherein X is a nitrogen-reactive
functional group (e.g. a "derivatising agent"). The second binding
partner is preferably labelled with a detectable label, such as a
dye, a fluorescent label, a radioactive isotope, a heavy metal or
an enzyme. The first binding partner may for example be a molecule
that is a ligand for a protein useful in the detection of the
resulting immobilized ligand, either stoichiometrically or
following amplification. The first binding partner may also be a
protein and the second binding partner a ligand for said
protein.
Examples of binding partners include ligand-protein pairs in common
use in ELISA assays. For example compound E may be reacted with a
biotinylation reagent, and after washing, detecting the now
immobilized biotin with streptavidin (or other avidins) that is
directly labelled with a detectable label, such as with a
fluorescent TAG, a radioactive isotope or a heavy metal, or with
streptavidin (or other avidins) that is conjugated to an enzyme
such as horseradish peroxidase that can catalyze a chemical
reaction that results in the production of a signal that can be
detected by spectrometry.
Other examples of binding partners are antibody-epitope pairs. Thus
the one binding partner could comprise an epitope and the other
binding partner could be an anti-body capable of binding said
epitope with high affinity, preferably an antibody specifically
binding said epitope.
F. Nucleic Acid Tags
In another embodiment of the invention the TAG is a nucleic acid.
Nucleic acids according to the invention may be any nucleic acid,
such as DNA or RNA, or analogues thereof such as LNA, PNA, HNA or
the like. Preferably the nucleic acid is DNA, preferably a DNA
oligomer. Preferably, said DNA is derivatised with an
nitrogen-reactive functional group, such as any of the
nitrogen-reactive functional groups mentioned herein above in the
section "Adding TAGs". It is preferred that the sequence of said
nucleic acid TAG is known or at least partially known, which will
enable the skilled person to readily detect said TAG using standard
methods.
The nucleic acid TAG may be any desirable length, preferably at
least a length which will allow specific detection. Thus preferably
the nucleic acid is at least 6 nucleotides, more preferably at
least 10 nucleotides, for example in the range of 10 to 5000
nucleotides long.
After addition of a nitrogen-reactive nucleic acid TAG to the
sugar, then the nucleic acid, such as the DNA oligomers can then be
detected directly on the solid support by hydridisation to their
complementary nucleic acids or essentially complementary nucleic
acid. By essentially complementary nucleic acids, is meant a
nucleic acid, which may hybridise to a given nucleic acid under
stringent conditions as for example described in Sambrook et al.,
1989, in "Molecular Cloning/A Laboratory Manual", Cold Spring
Harbor. Preferably, said complementary nucleic acids may be
attached to a detectable label. Said detectable label may for
example be a fluorescent label or a radioisotope or an enzyme,
preferably a fluorescent label. Thus, the nucleic acid TAG may for
example be detected by hybridisation to their complementary
fluorescently-labeled DNA. Alternatively, a nucleic acid TAG may be
amplified using conventional methods known in the art, such as
Polymerase Chain Reaction (PCR) or ligase chain reactin. Thus, the
immobilised nucleic acid TAG may be subjected to PCR reactions to
amplify the immobilized DNA oligomer which can be measured in
solution by a variety of well know techniques for quantification in
PCR. This process has particular value in the indirect detection
and quantification of very low amounts of
SugarCH--NH-Linker-Spacer-Solid present on the solid support.
Alternatively, the Sugar bound to DNA may be released to solution
by cleavage of the linker and thereafter amplified in solution by
for example PCR or detected in solution by virtue of specific
hybridisation to essentially complementary nucleic acids.
E.fwdarw.H Tethers
The derivatising agent according to the present invention may also
be a tether coupled to at least two functional groups. Such
bifunctional reagents will in general be of the structure
X-tether-Y or X-tether-Y.sub.p, wherein X is an nitrogen-reactive
functional group and Y is a second reactive functional group and
Y.sub.p is a latent reactive functional group or a protected
reactive group Y. The product of the reaction of compound E with
X-tether-Y (or X-tether-Yp) may for example have the general
structure of compound H of FIG. 1. The second reactive functional
group Y may be reactive to any of the types of reagents in use in
solid-phase synthesis. For example, the N in
SugarCH--NH-Linker-Spacer-Solid can be reacted with bifunctional
reagents (X-tether-Y) where one function reacts by making a bond to
the immobilized nitrogen (the nitrogen reactive functional group X)
and the other function can either be, or can be converted to (by
for example unmasking, deprotection or further reaction) a second
reactive functional group Y.
The tether may be any useful tether, for example alkyl, alkenyl or
alkynyl (which may be linear, branched or cyclic), aryl or any of
the aforementioned comprising amide bonds (NC(O)R) or
ethyleneglycol groups (--CH.sub.2CH.sub.2--O--) or substituted with
heteroatoms and their derivatives.
The second functional reactive group Y may for example be selected
from the group consisting of thiols, carboxyl groups, activated
carboxyl groups, disulfides, activated disulfides, alkylating
agents, alkenes, alkynes, aldehydes, ketones and azides. The
alkylating agent may for example be an alkyl halide or an
alpha-halo carbonyl group. Y.sub.p may for example be protected
amines or protected derivatives of any of the aforementioned groups
Y. Thus Y.sub.p may for example be selected from the group
consisting of protected amines, protected thiols, protected
carboxyl groups, protected aldehydes and protected ketones.
Protected reactive groups are herein denoted Y.sub.p, wherein
Y.sub.p may be deprotected to yield a functional reactive group Y.
Useful protecting groups can be found in Greene et al., 1999,
"Protective Groups in Organic Synthesis", 3rd. Ed., John Wiley and
Sons, New York, specifically for carbonyl groups (chapter 4, pp.
293-368), for carboxyl groups (chapter 5, pp. 369 453-), for thiols
(chapter 6, pp. 454-493) and for amino groups (chapter 7, pp.
494-653). Examples of protected amines include, but are not limited
to, those in common use in solid-phase peptide synthesis, such as
Fmoc, Boc, Alloc, p-nitrobenzyloxycarbonyl, trityl and substituted
trityl, o-nitrobenzyloxycarbonyl, N-sulfenyl or azido. However, the
second reactive functional group may be any functional groups Y, or
protected functional groups (Y.sub.p) that have been made to react
on the solid phase, such as examples well known in the art of solid
phase synthesis and the coupling of small molecules to solid
supports and surfaces. These functionalized groups can then
directly, or after deprotection to reactive species, capture a
second derivatising agent comprising a functional group (Z) capable
of reacting with the second functional group Y.
If Y in compound H contains an NH.sub.2 group, or on deprotection
can be made to contain an NH.sub.2 group, then any of the amine
reactive reagents described in E-goes-to-F (for example,
isothiocyanates) can be used to add a TAG to produce compounds of
the general structure I (FIG. 1).
The second derivatising agent made to react with any of the
functional groups Y in compound H (FIG. 1) may for example be
spectroscopic TAGs or any of the TAGs mentioned above in section
E.fwdarw.F, wherein said TAGs in stead of a nitrogen reactive
group, comprises or are derivatised with a functional group (Z)
capable of reacting with Y. They may also be small molecules like
drugs, imaging agents, peptides, proteins, enzymes and other
molecules exhibiting biological activities, nucleic acids such as
DNA or RNA
Said small molecules, imaging agents, peptides or nucleic acids
preferably comprises or are attached to a functional group Z,
capable of reacting with the given second functional reactive group
Y. The skilled person will readibly be able to identify useful
functional groups Y and Z. The second derivatising agent may also
be any of the above-mentioned TAGs described above in the sections
"TAGs with Spectroscopic properties", "Mass spectrometry TAGs",
"Binding partner TAGs" and "Nucleic acid TAGs", wherein said TAGs
in place of a nitrogen reactive functional group contains a
functional group Z capable of reacting with the functional group Y.
The functional group attached to the tether in H (FIG. 1) may also
be a latent or protected group (Y.sub.p) that can be converted by
chemical or enzymatic reaction into Y which may then react further
as described above. If this latent group can be converted to a
primary or secondary amine (i.e. Y will comprise the structure
--NH.sub.2 or --NH--), then any of the amine-reactive species
described in E.fwdarw.F above may be added to produce tagged
compounds of the structure I.
The methods of the invention may therefore comprise the step of
vii. Reacting the --NH-- group of the reactive sugar with a
bifunctional reagent of the structure X-tether-Y or
X-tether-Y.sub.p, wherein X is a nitrogen-reactive functional group
and Y is a second reactive functional group and Y.sub.p is a latent
functional group that can be converted to or deprotected to a
reactive functional group Y, thereby obtaining a sugar covalently
attached to said tether-Y or said tether-Y.sub.p.
This step is preferably performed using compound E of FIG. 1 as
starting material. Thus this step may for example generate a
compound of the general structure H of FIG. 1.
In embodiments of the invention wherein the bifunctional reagent is
of the structure X-ether-Y.sub.p, then preferably, the method
furthermore comprises the step of converting or deprotecting
Y.sub.p to obtain a reactive functional group Y. This step may be
performed before or after reacting X with --NH--, preferably it is
performed subsequent to reacting X with --NH--.
In addition the methods of the invention may furthermore comprise
the steps of viii. providing a second derivatising agent comprising
a functional group (Z) capable of reacting with Y ix. reacting the
functional groups Z and Y, thereby covalently attaching the second
derivatising agent to the sugar via a tether and the first
derivatising agent.
Alternatively, the methods of the invention may further comprise
the step of: viii. providing a particle selected from the group
consisting of eukaryotic cells, prokaryotic cells, microbial
organisms, micelles, phages, vira and nanoparticles, wherein the
particle comprises a functional group (Z) capable of reacting with
Y. ix. reacting the functional groups Z and Y, thereby covalently
attaching the particle to the sugar via the tether and the
agent.
Step ix. may thus generate a compound of the general structure I
outlined in FIG. 1 where the TAG is a particle. Provided that the
linker is a cleavable linker, the methods may further comprise the
step of cleaving the linker thereby for example generating a
compound of the general structure J of FIG. 1.
The product of the reaction of SugarCH--NH-Linker-Spacer-Solid
(e.g. compound E of FIG. 1) with bifunctional reagents X-tether-Y
for example has the general structure H and may contain, or can be
made to contain, further reactive groups that can form covalent
bonds to assemblies larger than molecules: for example bacteria,
phage, yeast, micelles, viruses, nanoparticles or eukaryotic or
prokaryotic cells. Cleavage of the linker then results in species
of the general formula SugarCH--N(assembly)-Linker, effectively
adding the sugar to the assembly. Thus, the sugar can in principle
be transferred from a solid support to an assembly.
Enzyme Treatment
If the solid support is biocompatible, i.e. permits contact with
biological macromolecules like enzymes without significantly
altering their activities, then the immobilised sugar molecule can
be acted on by enzymes that will alter its structure. The
immobilised sugar molecule may for example be a compound of any of
the general structures C, C.sub.red, D, E, F, H or I of FIG. 1.
Non-limiting examples of biocompatible solid supports includes
glass, PEGA, SPOCC or polysaccharide gels. Within this embodiment
it is preferred that the linker is relatively long, and thus it is
preferred that the linker comprises at least 2 atoms, preferably at
least 6 atoms, more preferably the linker comprises a chain of at
least 6 atoms, for example the longest chain of atoms within the
linker is at least 6 atoms long, such as in the range of 6 to 1000
atoms long. It is also preferred that the linker is
hydrophilic.
It is also possible to contact the sugars liberated into solution
by cleavage of a cleavable linker, such as the compounds G or J of
FIG. 1 with biological macromolecules, such as enzymes.
The enzymes can belong to any class that can act on carbohydrates,
for example glycosidases, glycosyltransferases, and enzymes that
modify the alcohol groups by acylation, phosphorylation, sulfation
or oxidation. Alternatively, if the sugars are already substituted
on --OH groups, such as acylated, phosphorylated or sulphated, then
deacylases, phosphatases and sulfatases can alter their structures.
Thus the methods of the invention may furthermore comprise the step
of contacting the sugar (for example any of the compounds C,
C.sub.red, D, E, F, G, H, I or J of FIG. 1) with one or more
enzymes selected from the classes of glycosyltransferases,
sulfatases, phosphorylases, sulfotransferases, phosphotransferases,
glycosynthases and transglycosidases, thereby converting said sugar
into a new structure. In a preferred embodiment the methods
furthermore comprise the step of contacting the sugar (for example
any of the compounds C, C.sub.red, D, E, F, G, H, I or J of FIG. 1)
with one or more glycosidases, thereby generating a new reducing
sugar, provided that the first sugar is a substrate for said
glycosidase(s).
An example would include the incubation of uncapped
Sugar-C.dbd.N-Linker-Spacer-Solid (for example, compounds C of FIG.
1), which still contains free --NH.sub.2 groups, with an
exoglycosidase causing the decrease in the length of the sugar by
one monosaccharide residue. The cleavage of this monosaccharide
residue leaves an oligosaccharide attached to the solid support
that is one sugar unit shorter, and produces a reducing sugar which
can be captured by the same or a different solid support, such as a
solid support of the general structure B in FIG. 1, which can
subsequently be submitted to any of the manipulations described
above in B to J.
Thus the methods of the invention may furthermore comprise the
steps of
a) providing one or more enzymes that can act on carbohydrates
b) contacting the sugar with said one or more enzymes
These steps may be performed at any given time during the method.
The enzymes may be any of the enzymes described in the present
section.
In a particular embodiment the enzyme is a glycosidase and the
method described herein above in the summary section comprises the
further steps of:
iii.a) providing one or more glycosidases that can act on
carbohydrates
iii.b) contacting the sugar with said one or more glycosidases,
thereby generating a new reducing sugar, provided that the first
sugar is a substrate for said glycosidase(s).
iii.c) immobilising newly generated reducing sugar(s) on a solid
support.
The steps iii.a-iii.c may be carried out following step iii. of the
method outlined in the section "Summary of the invention" herein
above. However, the steps iii.a to iii.c may also be carried out
following any of steps iv, v, vi or vii of said method.
Accordingly, steps iii.a-iii.c may be carried out on any of the
immobilized sugars exemplified by structures C, C.sub.red, D, E, F,
H or I of FIG. 1.
In particular, said newly generated reducing sugars may be
immobilised to free --NH.sub.2 groups of the same solid support or
on another solid support. Said other solid support may for example
either be unsubstituted or carry an immobilised reference standard.
It is preferred that said other solid support is a solid support as
described herein above, and that the solid support is attached to a
linker (optionally via a spacer), wherein said linker comprises a
capture group (see detailed description of linkers, capture groups
and spacers herein above).
Of particular value is the reduction and fluorescence labeling of
the glycosidase product and the released monosaccharide on the same
or a different solid support, for purposes of obtaining structural
information. A specific example includes the capture of
Gal-GlcNAc-Gal-Glc (lacto-N-tetraose, LNT) on
NH.sub.2-Linker-Spacer-Solid of structure B (FIG. 1), incubation of
the captured and immobilized LNT (an example of a compound of
structure C of FIG. 1) with beta-galactosidase followed by capture
of the released galactose on the same solid support (C) to yield a
mixture of unreacted Gal-GlcNAc-Gal-GlcC.dbd.N-Linker-Spacer-Solid,
and the products of the reaction which are
GlcNAc-Gal-GlcC.dbd.N-Linker-Spacer-Solid and
Gal-C.dbd.N-Linker-Spacer-Solid. Capping, reduction, fluorescence
tagging with TRITC and cleavage form the solid as described in step
F.fwdarw.G above then allows confirmation that the immobilized LNT
had a terminal beta-galactose residue, by co-migration of the
trisaccharide and monosaccharide products with known standards.
Many useful glycosidases are described in the art, for example any
of the glycosidases described in U.S. Pat. No. 5,100,778 or
WO92/19974 may be employed with the present invention.
If the solid support is biocompatible, then the unreacted
--NH.sub.2 groups in Sugar-C.dbd.N-Linker-Spacer-Solid (e.g.
compound C, FIG. 1) can be capped (for example with acetic
anhydride as described in C.fwdarw.D above) and then exposed to
carbohydrate-active enzymes, or further reduced to
SugarCH--NH-Linker-Spacer-Solid (as described in section D.fwdarw.E
above) and then exposed to carbohydrate-active enzymes.
Alternatively, compound C of FIG. 1 can be reduced to C.sub.red and
then exposed to carbohydrate active enzymes. The
SugarCH--NH-Linker-Spacer-Solid (e.g. compound E, FIG. 1) can be
further tagged (as described in sections E.fwdarw.F herein above)
to yield SugarCH--N(TAG)-Linker-Spacer-Solid (e.g. compound F, FIG.
1), and then exposed to carbohydrate-active enzymes. In any of
these processes, the product of the enzyme reaction that remains
attached to the solid support can be further manipulated according
to the methods of the invention or cleaved by reaction at the
linker, for further analysis. Any product of the enzyme reaction
that results in cleavage of fragments of the immobilized sugar will
appear in solution, where it may be further investigated using
established techniques of analytical chemistry or, in the case
where it is itself a reducing sugar, may be subjected to the
manipulations described for the generic sugar A in FIG. 1.
The individual sugars may be detected by capillary gas
chromatography (GC), microcolumn supercritical fluid chromatography
(SFC), microcolumn liquid chromatography (LC), high performance
liquid chromatography (HPLC), high performance capillary
electrophoresis (HPCE), ion-exchange chromatography or
mass-spectrometry. Detection of individual sugars may be done
before or after labelling with a derivatising agent, and either in
solution or on the solid phase.
Detection Agents
In one embodiment of the invention, the method comprises the steps
of viii. contacting the sugar with a detection agent capable of
associating with said sugar ix. detecting the detection agent
Preferably, said sugar is immobilised on a solid support as
described herein above, and thus for example a compound of the
general structure C, C.sub.red, D, E, F, H or I of FIG. 1 may be
contacted with said detection agent. It is also possible that said
sugar has been released from the solid support by cleavage of a
cleavable linker, as thus a compound of the general structure G or
J may also be contacted with said detection agent.
The detection agent may be any agent capable of associating with
said sugar. Preferred detection agents are compounds capable of
associating with sugars with much higher affinity than with any
other compounds, such as compounds having at least a 2-fold, such
as at least a 5-fold higher affinity for sugars, than for any other
compound.
In addition it is preferred that said detection agent is directly
or indirectly detectable by a method known to the skilled person.
For example the detection agent may itself be for example a
fluorescent or coloured compound. The detection agent may also be a
compound for which easy detection methods are available.
In one embodiment of the invention the detection agent comprises an
aryl boronate or heteroaryl boronate where the aryl moiety is
substituted with a spectroscopically active group such as a
fluorescent TAG or any of the other detectable TAGs described
herein above in the section "F. TAGs with spectroscopic
properties".
In another embodiment the detection agent is a polypeptide,
preferably a polypeptide selected from the group consisting of
lectins, selectins and other carbohydrate binding proteins, toxins,
receptors, antibodies and enzymes. When the detection agent is a
polypeptide, said polypeptide may be coupled to a detectable label,
such as an enzyme or a fluorescent compound. The polypeptide may
also be detected by the aid of antibodies or similar high affinity
compounds.
EXAMPLES
The following are illustrative examples of the methods of the
invention and should not be considered as limiting for the
invention. Unless otherwise clear from the context, capital letters
A, B, C, C.sub.red, D, E, F, G, H, I and J refers to the general
structures outlined in FIG. 1.
Experimental
1. Examples of A
Reducing Sugars Used in the Present Work
The structures of the reducing sugars captured by solid supports B
are shown in FIG. 2. These included the monosaccharides D-Glc (1)
and D-Gal (2), the disaccharide N-acetyllactosamine (LacNAc, 3),
the trisaccharide maltotriose (maltotriose G3, 4) and the
tetrasaccharide lacto-N-tetraose (LNT, 5). Samples 6 and 7
contained mixtures of the monosaccharides Fuc:Man:GalNAc in ratios
of 2:3:1 and 1:3:2, respectively. Sample 8 contained a 1:1 mixture
of Gal (2) and LNT (5). Sample 9 contained an approximately
equimolar mixture of maltobiose (G2), maltotriose (G3),
maltotetraose (G4), maltopentaose (G5), maltohexaose (G6) and
maltoheptaose (G7). Sample 10 consisted of the N-linked
oligosaccharide chains released from ribonuclease B (Sigma) by the
action of PNGase F (product number 1365177, Boehringer Mannheim
GmbH, Germany).
2. Linkers, Spacers and Tagged-Sugar Reference Standards
2.1 Linker and Spacer
The synthesis of the cleavable linker and the structure of the
spacer are shown in FIG. 3 and described below.
12: N-Fmoc-4-aminooxymethyl-benzoic acid
To a solution of 4-aminooxymethyl-benzoic acid, hydrochloride
11.sup.1 (2.0 g, 0.010 mol) in dioxane (20 mL) and half saturated
Na.sub.2CO.sub.3 solution (20 mL) was added Fmoc-Cl (2.8 g, 0.011
mol) and the mixture was stirred for 2 h. Ethyl acetate (100 mL)
was added and the pH of the aqueous phase was adjusted to 1-3 by
careful addition of HCl.sub.(conc.). The mixture was poured in to a
separating funnel and the organic phase was isolated, washed once
with water (100 mL), dried over Na.sub.2SO.sub.4 and the solvent
was removed on a rotavap to give an oil that solidified upon
standing. The crude product was purified by flash column
chromatography (petroleum ether, ethyl acetate, AcOH 60:40:1).
Yield: 3.5 g (92%) .sup.1H-NMR (250 MHz, DMSO-d6) =4.05 (1H, t,
J=6.3 Hz), 4.27 (2H, d, J=6.3 Hz), 4.51 (2H, s), 7.08-7.22 (6H, m),
7.46 (2H, d, J=7.4 Hz), 7.66 (2H, d, J=7.1 Hz), 7.72 (2H, d, J=8.4
Hz), 10.29 (1H, br. s), 12.78 (1H, br. s). .sup.13C-NMR (63 MHz,
DMSO-d6) =47.04, 66.03, 76.91, 120.51, 125.41, 127.45, 128.03,
128.89, 129.33, 129.63, 130.82, 141.19, 144.01, 157.12, 167.48. MS
(ES) m/z=389 (MH.sup.+). .sup.1The material was prepared as
previously described: Deles, J. et al.; PJCHDQ; Pol. J. Chem.; EN;
53; 1979; 1025-1032
13: Reaction of N-Fmoc-4-aminooxymethyl-benzoic acid (12) with
t-butyl bromoacetate
N-Fmoc-4-aminooxymethyl-benzoic acid (12) (1.0 g, 2.57 mmol) was
dissolved in DMF (15 mL) and Cs.sub.2CO.sub.3 (0.42 g, 1.28 mmol,
Aldrich) was added followed by stirring for 5 min at rt. tert-Butyl
bromoacetate (0.55 g, 2.28 mmol, Fluka) was added and the mixture
was heated to 50.degree. C. for 30 min and then cooled to rt again.
CH.sub.2Cl.sub.2 (70 mL) was added and the mixture as poured in to
a separating funnel and washed with half saturated NaHCO.sub.3
solution (3.times.50 mL) and then water (2.times.50 mL), dried over
MgSO.sub.4. The solvent was removed under reduced pressure to give
the crude product as an oil. After flash column chromatography
(20-40% ethyl acetate in petroleum ether) a white solid was
obtained in a yield of 1.15 g (89%). .sup.1H-NMR (250 MHz,
CDCl.sub.3) =1.37 (9H, s), 4.06 (1H, t, J=6.7 Hz), 4.37 (2H, d,
J=6.7 Hz), 4.61 (2H, s), 4.67 (2H, S), 7.11-7.18 (2H, m), 7.22-7.27
(4H, m), 7.43 (2H, d, J=7.5 Hz), 7.60 (2H, d, J=7.3 Hz), 7.75 (1H,
s), 7.93 (2H, dd, J=1.7 Hz, 6.6 Hz). .sup.13C-NMR (63 MHz,
CDCl.sub.3) =26.31, 45.28, 59.95, 65.52, 75.99, 80.84, 118.30,
123.27, 125.41, 126.10, 126.93, 127.23, 128.30, 139.29, 139.58,
141.73, 155.70, 163.94, 165.15. MS (ES) m/z=542 (MK.sup.+).
14: Preparation of Linker
The white solid 13 (1.15 g) obtained in the previous experiment was
stirred in a 50% solution of CF.sub.3CO.sub.2H in CH.sub.2Cl.sub.2
(30 mL) for 3 h and evaporated to dryness. The oily residue was
taken up in a small amount of ethyl acetate and the product was
precipitated as a fine white powder by slow addition of hexanes to
the solution. The product was filtered and washed a couple of times
with hexanes and dried under vacuum to give the desired product in
an almost quantitative yield (1.0 g, 98%). .sup.1H-NMR (250 MHz,
DMSO-d6) =4.07 (1H, t, J=6, 3 Hz), 4.28 (2H, d, J=6, 3 Hz), 4.53
(2H, s), 4.62 (2H, S), 7.07-7.14 (2H, m), 7.17-7.26 (4H, m), 7.46
(2H, d, J=7.4 Hz), 7.66 (2H, d, J=7.2 Hz), 7.77 (2H, d, J=8.3 Hz),
10.30 (1H, br. s). .sup.13C-NMR (63 MHz, DMSO-d6) =47.04, 61.62,
66.04, 76.79, 120.50, 125.41, 127.46, 128.03, 129.05, 129.69,
141.19, 142.20, 144.00, 157.12, 165.50, 169.47. MS (ES) m/z=446
(M-H.sup.+). HRMS (ES) calculated
(C.sub.25H.sub.21NO.sub.7Na.sup.+): 470.1210 found: 470.1224.
2.2 Synthesis of Tetramethylrhodamine (TMR)-Tagged Monosaccharide
Standards of the General Structure G.
The 8 monosaccharides D-Glc, D-Gal, D-Man, D-Xyl, D-GlcNAc,
D-GalNAc, L-Fuc and D-GlcA were used. The general synthetic scheme
is shown in FIG. 4 for D-Gal (2), and the structure of the product
21 is shown in FIG. 4 and is abbreviated GalCH.sub.2--N(R)-TMR as
shown. The structures of all eight SugarCH.sub.2--N(R)-TMR
monosaccharide derivatives prepared are shown in FIG. 5.
16: Reaction of N-Fmoc-4-aminooxymethyl-benzoic acid (12) with
Benzylbromide
N-Fmoc-4-aminooxymethyl-benzoic acid (12, 2.0 g, 5.14 mmol) was
dissolved in DMF (30 mL) and Cs.sub.2CO.sub.3 (0.84 g, 2.57 mmol)
was added followed by stirring for 5 min at rt. Benzyl bromide
(1.05 g, 6.17 mmol) was added and the mixture was allowed to stir
for another 30 min at rt. Water (200 mL) was added and the mixture
was extracted with CH.sub.2Cl.sub.2 (2.times.100 mL). The combined
organic phases were washed with water (3.times.50 mL), dried over
MgSO.sub.4, evaporated to dryness to yield an oil which was used
without further characterization in the next experiment.
17: Removal of Fmoc-Group from
benzyl-(N-Fmoc-4-aminooxymethyl)-benzoate
The crude product (16) obtained in the previous experiment was
stirred with 20% piperidine in DMF (20 mL) for 1 min and passed
through a bed of silica gel to remove the majority of DMF and
piperidine by suction. The product was eluted from the bed of
silica gel with a mixture of ethyl acetate and pet. ether (1:1) and
concentrated on a rotavap. Further purification was achieved by
flash column chromatography (ethyl acetate, petroleum ether 1:1) to
give a clear oil in a yield of 1.16 g (88%, two steps). .sup.1H-NMR
(250 MHz, CDCl.sub.3) .delta.=4.66 (2H, s), 5.29 (2H, s), 7.25-7.39
(7H, m), 7.99 (2H, dd, J=1.7 Hz, 6.5 Hz). .sup.13C-NMR (63 MHz,
CDCl.sub.3) .delta.=67.11, 77.59, 128.32, 128.57, 128.66, 129.02,
129.19, 130.32, 136.48, 143.47, 166.64. MS (MALDI-TOF) m/z=258
(MH.sup.+).
General procedure for preparation of TMR labelled monosaccharide
standards exemplified by the preparation of galactose standard.
18: Oxime Formation Between Galactose and
benzyl-(4-aminooxymethyl)-benzoate
Galactose (90 mg, 0.50 mmol) was dissolved in a mixture of DMSO and
AcOH (7:3, 3 mL) and (17, 128 mg, 0.50 mmol) was added. The mixture
was heated for 3 h at 55.degree. C. and poured into water (30 mL)
and cooled on an ice bath which caused the product to crystallize
as fine white crystals. The product was isolated by filtration,
washed with water (2.times.10 mL) and dried under vacuum to yield
the 170 mg (83%) of product as a single isomer. .sup.1H-NMR (250
MHz, DMSO-d6) .delta.=3.38-3.55 (4H, m), 3.67-3.75 (1H, m),
4.27-4.33 (1H, m), 5.12 (2H, s), 5.37 (2H, s), 7.36-7.52 (7H, m),
7.56 (1H, d, J=7.6 Hz), 8.00 (2H, d, J=8.1 Hz). .sup.13C-NMR (63
MHz, DMSO-d6) .delta.=63.40, 66.52, 68.37, 69.21, 70.04, 72.63,
74.27, 128.25, 128.33, 128.49, 128.91, 129.13, 129.67, 136.52,
144.22, 154.00, 165.78. MS (MALDI-TOF) m/z=442 (MNa.sup.+)
19: Reduction of "galactose-oxime" (18) with BH.sub.3-pyridine
The oxime (18,150 mg, 0.36 mmol) obtained in the previous
experiment was dissolved in methanol (10 mL). BH.sub.3-pyridine
(225 .mu.L, 8 M solution in pyridine, 1.80 mmol, Fluka) and
CCl.sub.3CO.sub.2H (0.50 mL, 50% aqueous solution) were added and
the mixture was stirred for 1 h at rt. The reaction mixture was
carefully poured into a half-saturated solution of Na.sub.2CO.sub.3
(20 mL) and extracted with a 1:1 mixture of ether and hexanes
(2.times.10 ml) to remove excess borane reagent. The pH was now
adjusted to 2-3 by careful addition of HCl.sub.(conc.) and the
volume was reduced to half of the original on a ratovap. During the
evaporation the product separated out as nice white crystalline
solid, which was filtered of, washed with water (2.times.10 mL),
ether (2.times.10 mL) and finally the product was dried under
vacuum to give 112 mg (75%) of pure product. .sup.1H-NMR (250 MHz,
DMSO-d6) .delta.=3.31-3.33 (2H, m), 3.40-3.55 (5H, m), 3.74 (1H, t,
J=6.3 Hz), 5.24 (2H, s), 5.37 (2H, s), 7.36-7.50 (5H, m), 7.60 (2H,
d, J=8.2 Hz), 8.04 (2H, d, J=8.2 Hz). .sup.13C-NMR (63 MHz,
DMSO-d6) .delta.=53.34, 63.40, 64.73, 66.68, 69.37, 70.19, 70.89,
74.20, 128.36, 128.53, 128.92, 129.47, 129.87, 130.27, 136.41,
139.73, 165.62. MS (MALDI-TOF) m/z=422 (MH.sup.+).
20: Labelling of Reduced Product (19) Using TRITC
A small amount of the product (19, 4.2 mg, 10 .mu.mol) prepared in
previous experiment was dissolved in DMF (1 mL) and TRITC (4.4 mg,
10 .mu.mol) was added. After stirring for 1 h water (10 mL) was
added and the precipitated product was redissolved by addition of
HCl.sub.(conc.) and the clear red solution was applied to a small
C-18 Sep-Pak column to bind the product. The column was flushed
several times with water (total volume 30 mL) followed by release
of the product with methanol (5 mL). The volume was reduced to
approximately 0.5 mL and the material was purified by flash column
chromatography on silica gel with a mixture of CH.sub.2Cl.sub.2,
methanol, water, AcOH (70:20:9:1). The identity of the compound was
confirmed by MS and used directly in the next experiment. MS
(MALDI-TOF) m/z=865 (MH.sup.+).
21: Hydrolysis of Ester Protecting Group to Give Final Standard
All the material (20) obtained in the previous experiment was
dissolved in 1 M LiOH (1 mL) and stirred for 30 min followed by
addition of water (10 mL) and acidification with HCl.sub.(conc.) to
give a clear red solution. The product was desalted on a small C-18
Sep-Pak column by repeated washings with water (total volume 30 mL)
followed by release of the product with methanol (5 mL). The volume
was reduced to approximately 0.5 mL and the product was purified by
flash column chromatography on silica gel with a mixture of
chloroform, methanol, water (120:85:20). The identity of the
compound was confirmed by high resolution MS and its purity was
analysed using CE. HRMS (ES) calculated
(C.sub.39H.sub.43N.sub.4O.sub.11S): 775.2649 found: 775.2700
Standards of the remaining monosaccharides (glucose, mannose,
N-acetylglucosamine, N-acetylgalactosamine, xylose, fucose and
glucuronic acid) were prepared using the same protocol as described
for galactose in similar yields and purity. The compounds'
identities were likewise confirmed by high resolution mass
spectroscopy (see table below). Each compound gave a single peak in
CE, and all 8 compounds (21-28) could be resolved in CE (FIG.
10).
TABLE-US-00001 III. Found I. Standard II. Calculated mass mass
Variation Galactose (21) 775.2649
(C.sub.39H.sub.43N.sub.4O.sub.11S) 775.2700 .DELTA. = 6.58 ppm
Glucose (22) 775.2649 (C.sub.39H.sub.43N.sub.4O.sub.11S) 775.2696
.DELTA. = 6.06 ppm Mannose (23) 775.2649
(C.sub.39H.sub.43N.sub.4O.sub.11S) 775.2695 .DELTA. = 5.93 ppm
Xylose (24) 745.2543 (C.sub.38H.sub.41N.sub.4O.sub.10S) 745.2536
.DELTA. = 0.94 ppm Fucose (25) 759.2700
(C.sub.39H.sub.43N.sub.4O.sub.10S) 759.2728 .DELTA. = 3.69 ppm
N-Acetylglu- 816.2914 (C.sub.41H.sub.46N.sub.5O.sub.11S) 816.2983
.DELTA. = 8.45 ppm cosamine (26) N-Acetylgalac- 816.2914
(C.sub.41H.sub.46N.sub.5O.sub.11S) 816.2995 .DELTA. = 9.92 ppm
tosamine (27) Glucuronic 789.2441
(C.sub.39H.sub.41N.sub.4O.sub.12S) 789.2507 .DELTA. = 8.36 ppm acid
(28)
3. Examples of B
Preparation and Nomenclature of Solid Supports
Solid supports of general structure B (FIG. 1) were prepared using
both PEGA resin (PEGA 1900, Versamatrix A/S) and controlled-pore
glass (CPG). B.sup.P indicates a PEGA resin where the linker is
attached directly to the amino groups on the commercial resin
without a spacer. B.sup.0, B.sup.1 and B.sup.2 indicate CPG where
the linker has been attached through 0, 1 and 2 spacers
respectively to aminopropylated glass (AMP-CPG, CPG-Biotech). The
structures of the four solid supports are shown in FIG. 6.
3.1 B.sup.p (PEGA Resin of General Structure B)
1 g of commercial PEGA 1900 resin (loading of amino groups: 0.23
mmol/g) swelled in methanol was washed repeated time with DMF to
ensure complete removal of the methanol. The linker (14) (308 mg,
0.69 mmol), TBTU (207 mg, 644 mmol) and DIPEA (119 mg, 0.92 mmol)
were mixed in DMF (10 mL) and left to pre-activate for 5 min before
adding the mixture to the resin. After 3 h the reagents were
removed by suction and the resin was washed with CH.sub.2Cl.sub.2
(5.times.20 mL).
A small portion of the resin was taken out for Kaiser test which
confirmed a successful coupling of the linker to the resin.
Likewise, the loading of linker on the resin was determined as
described in example 3.3 and found to be approximately 0.20 mmol/g
by comparison with a standard curve. The hydroxylamine protecting
group (Fmoc) was now removed from the remaining resin by treatment
with 20% piperidine in DMF (15 mL for 2 min and 15 mL for 18 min)
followed by extensive washings with DMF (5.times.20 mL) and
CH.sub.2Cl.sub.2 (7.times.20 mL). The resin was dried under high
vacuum for 24 h to give the final PEGA resin (B.sup.P) which was
used for all subsequent experiments.
3.2 B.sup.0, B.sup.1 and B.sup.2 (Controlled Pore Glass, CPG)
B.sup.0: Coupling of Linker 14 with CPG-NH.sub.2
AMP CPG (250 mg, loading=50.1 .mu.mol/g, 0.0125 mmol. Millipore,
product no. AMP1400B) was washed with DMF (3.times.2 mL), 50% DIPEA
in DMF (3.times.2 mL), and DMF (3.times.2 mL). The beads were
treated with a mixture of 14 (17 mg, 0.038 mmol), TBTU (12 mg,
0.037 mmol), and DIPEA (8.6 .mu.L, 0.05 mmol) in DMF at rt over
night. The beads were washed with DMF (3.times.2 mL),
CH.sub.2Cl.sub.2 (3.times.2 mL), and treated with 50% of Ac.sub.2O
in pyridine for 15 min at rt, washed with CH.sub.2Cl.sub.2
(3.times.2 mL), DMF (3.times.2 mL), CH.sub.2Cl.sub.2 (3.times.2
mL), and dried. The loading was determent to 14.2 .mu.mol/g as
described for B.sup.1. The Fmoc group was removed using 20%
piperidine in DMF for 2.times.10 min at rt and washed with, DMF
(3.times.2 mL), CH.sub.2Cl.sub.2 (3.times.2 mL), and ethanol
(3.times.2 mL), and CH.sub.2Cl.sub.2 (3.times.2 mL). The resin was
dried in vacuum.
B.sup.1: Coupling of One Spacer 15 and Linker 14 with
CPG-NH.sub.2
AMP CPG (2.26 g, loading=50.1 .mu.mol/g, 0.11 mmol. Millipore,
product no. AMP1400B) was washed with DMF (3.times.2 mL), 50% DIPEA
in DMF (3.times.2 mL), and DMF (3.times.2 mL). The beads were
treated with a mixture of 15 (168 mg, 0.34 mmol), TBTU (105 mg,
0.33 mmol), and DIPEA (78 .mu.L, 0.45 mmol) in DMF for 3 h at rt.
The resin was washed with DMF (3.times.5 mL), CH.sub.2Cl.sub.2
(3.times.5 mL), and treated with 50% Ac.sub.2O in pyridine for 15
min at rt. The beads were washed with CH.sub.2Cl.sub.2 (3.times.5
mL), DMF (3.times.5 mL), CH.sub.2Cl.sub.2 (3.times.5 mL), and
treated with 50% TFA in CH.sub.2Cl.sub.2 for 2 h at rt. Washed with
CH.sub.2Cl.sub.2 (3.times.5 mL), DMF (3.times.5 mL), and
CH.sub.2Cl.sub.2 (3.times.5 mL). 1/3 of the beads (2.5 mL,
.about.0.70 g, .about.35 .mu.mol) were washed with DMF (3.times.5
mL). Treated with 14 (47 mg, 0.11 mmol), TBTU (33 mg, 0.10 mmol),
and DIPEA (34 .mu.L, 0.20 mmol) in DMF over night at rt. The beads
were washed with DMF (3.times.5 mL), CH.sub.2Cl.sub.2 (3.times.5
mL), and treated with 50% Ac.sub.2O in pyridine for 15 min at rt,
washed with CH.sub.2Cl.sub.2 (3.times.5 mL), DMF (3.times.5 mL),
CH.sub.2Cl.sub.2 (3.times.5 mL), and dried. The loading was
determined (29 .mu.mol/g) and the beads were treated with 20%
piperidine in DMF at rt for 2.times.10 min. The beads were washed
with, DMF (3.times.2 mL), CH.sub.2Cl.sub.2 (3.times.2 mL), and
ethanol (3.times.2 mL), CH.sub.2Cl.sub.2 (3.times.2 mL), and
dried.
B.sup.2: Coupling of Two Spacers 15 and Linker 14 with
CPG-NH.sub.2
2/3 of the resin with one spacer from B.sup.1 (5.5 mL, .about.1.54
g, .about.77 .mu.mol) was washed with DMF (3.times.5 mL). The beads
were treated with a mixture of 15 (114 mg, 0.23 mmol), TBTU (72 mg,
0.22 mmol), and DIPEA (53 .mu.L, 0.31 mmol) in DMF over night at
rt. The beads were washed with DMF (3.times.5 mL), CH.sub.2Cl.sub.2
(3.times.5 mL), and treated with 50% Ac.sub.2O in pyridine for 15
min at rt, washed with CH.sub.2Cl.sub.2 (3.times.5 mL), DMF
(3.times.5 mL), CH.sub.2Cl.sub.2 (3.times.5 mL), and treated with
50% CF.sub.3CO.sub.2H in CH.sub.2Cl.sub.2 for 2 h at rt, washed
with CH.sub.2Cl.sub.2 (3.times.5 mL), DMF (3.times.5 mL), and
CH.sub.2Cl.sub.2 (3.times.5 mL). Half the amount of the beads
(.about.42 .mu.mol) were washed with DMF (3.times.5 mL) and treated
with 14 (56 mg, 0.13 mmol), TBTU (39 mg, 0.12 mmol), and DIPEA (29
.mu.L, 0.17 mmol) at rt over night. The beads were washed with DMF
(3.times.5 mL), CH.sub.2Cl.sub.2 (3.times.5 mL) and treated with
50% Ac.sub.2O in pyridine for 15 min at rt, washed with
CH.sub.2Cl.sub.2 (3.times.5 mL), DMF (3.times.5 mL),
CH.sub.2Cl.sub.2 (3.times.5 mL) and dried. The loading was
determent as described for B.sup.1 to 36 .mu.mol/g. The resin was
covered with 20% piperidine in DMF at rt for 2.times.10 min, washed
with, DMF (3.times.5 mL), CH.sub.2Cl.sub.2 (3.times.5 mL), ethanol
(3.times.5 mL) 3.times.CH.sub.2Cl.sub.2 (3.times.5 mL), and dried
in vacuum.
3.3 Example of the Estimation of the Loading of Capture Groups on
Solid Supports of General Structure B (FIG. 1)
Seven concentrations of Fmoc-Gly-OH in 20% piperidine in DMF (0.0
mM, 0.1 mM, 0.25 mM, 0.5 mM, 1.0 mM, 1.5 mM, 2.0 mM) were prepared.
The UV absorbance of released fulvene were measured at 290 nm using
nonodrop technology (Saveen Werner Nanodrop, Model: ND-1000, Serial
No: 0911). The absorbance was plotted against the concentration
giving a linear curve with slope 0.581 mM.sup.-1.
Fmoc protected B.sup.1 beads (4.8 mg) were treated with 20%
piperidine in DMF (200 .mu.L) for 10 min. The UV absorbance at 290
nm was measured to 0.410 and the liberated fulvene concentration
was calculated
.times..times..times..times..times..times..times. ##EQU00001##
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mes..times. ##EQU00001.2## .times. ##EQU00001.3##
.times..times..times..times..times..times..times..times..times..times..ti-
mes..times..times..times..times..times..times..times..times..times..times.-
.times..times..times. ##EQU00001.4##
4. Examples of A+B.fwdarw.C, and Processing of C
4.1 Variation of Capture Conditions Using Glucose as the Reducing
Sugar and B.sup.2 as the Solid Support.
Various solvents, temperatures and additives were examined in order
to find preferable conditions for the capture of reducing sugars on
solid supports of general structure B.sub.1 to produce C. D-Glc was
used as the model compound, as the amount of uncaptured Glc in
solution could be readily estimated with high sensitivity using the
Amplex Red assay from Molecular Probes. The amount of Glc captured
was thus calculated to be the amount added minus the amount
remaining in solution after incubation.
15-20 mg of beads (B.sup.2) were treated with a solution of glucose
under different conditions. After end reaction time the supernatant
was removed and the amount of unreacted glucose was estimated using
the Amplex Red Glucose/Glucose Oxidase Assay Kit (A-22189,
Molecular Probes).
TABLE-US-00002 Capture of glucose using different solvents,
concentrations, temperatures and reaction times No Glc Vol [Glc]
Solvent pH Temp Time Capture C.sup.2A.sub.1 1 eq 108 .mu.L 4.0 mM
Citrate* 5 37.degree. C. 4 h 8% C.sup.2A.sub.2 1 eq 108 .mu.L 4.0
mM DMSO/AcOH 3 37.degree. C. 4 h 2% C.sup.2A.sub.3 1 eq 108 .mu.L
4.0 mM Citrate 5 37.degree. C. on 16% C.sup.2A.sub.4 1 eq 108 .mu.L
4.0 mM DMSO/AcOH 3 37.degree. C. on 21% C.sup.2A.sub.5 1 eq 108
.mu.L 4.0 mM Citrate 5 55.degree. C. 4 h 13% C.sup.2A.sub.6 1 eq
108 .mu.L 4.0 mM DMSO/AcOH 3 55.degree. C. 4 h 16% C.sup.2A.sub.7 1
eq 108 .mu.L 4.0 mM Citrate 5 55.degree. C. on 35% C.sup.2A.sub.8 1
eq 108 .mu.L 4.0 mM DMSO/AcOH 3 55.degree. C. on 35% C.sup.2A.sub.9
0.1 eq 104 .mu.L 0.4 mM Citrate 5 55.degree. C. on 85%
C.sup.2A.sub.10 0.1 eq 104 .mu.L 0.4 mM DMSO/AcOH 3 55.degree. C.
on 94% *0.1 M citrate/phosphate buffer, pH 5.0.
4.2 Capture, Processing and Analysis of Representative Reducing
Sugars on B.sup.P.
The following designations are used below to describe compounds of
the general structures C, C.sub.red, D, E, F, G, H, I and J (FIG.
1). The particular letter describing the particular structure under
discussion is given first, e.g. C or E. The next superscript number
refers to which of the four solid supports shown in FIG. 6 was
used. Thus, by way of example if B.sup.P (FIG. 6) is used to
capture a sugar, then the product will have the general structure C
which is further designated as C.sup.P. The next number refers to
which of the ten samples of reducing sugars shown in FIG. 2 was
captured. Thus, C.sup.P2 refers to the product of the PEGA resin
B.sup.P that has captured galactose (compound 2 of FIG. 2). In the
same way, D.sup.25 would refer to the product obtained when the
solid support B.sup.2 has captured the tetrasaccharide LNT (5, FIG.
2) to give C.sup.25, and then been further capped to D.sup.25.
4.2.1 Capture and Processing of Reducing Sugar 3
C.sup.P3: Capture of LacNAc (3) on B.sup.P
A stock solution was made by first dissolving LacNAc (3) (38 mg,
0.10 mmol) in water (1.0 mL) and then diluting the sample 10 times
with a mixture of DMSO and AcOH (7:3, 9 mL) to give a 10 mM stock
solution of LacNAc (3). 40 .mu.L (0.40 .mu.mol) was then taken from
the stock solution and diluted further with the mixture of DMSO and
AcOH (7:3, 150 .mu.L) and the whole was added to B.sup.P (10 mg, 2
.mu.mol) and left to incubate at 60.degree. C. over night. The
resin was washed several times: DMF (5.times.0.5 mL), methanol
(5.times.0.5 mL) and used directly in the next experiments.
D.sup.P3: Capping of C.sup.P3 with Acetic Anhydride
All the resin obtained in experiment C.sup.P3 was treated with a
mixture of Ac.sub.2O and methanol 1:1 (0.4 mL) for 1 h followed by
washing with DMF (5.times.0.5 mL), water (2.times.0.5 mL), methanol
(5.times.0.5 mL) and used directly in the next experiment.
E.sup.P3: Reduction of D.sup.P3 with BH.sub.3-pyridine
The resin obtained in experiment D.sup.P3 was covered with methanol
(0.1 mL) and BH.sub.3-pyridine (20 .mu.L, 8 M in pyridine) was
added followed by addition of 50% CCl.sub.3CO.sub.2H acid in water
(40 .mu.L). The reaction was left to proceed for 2 h at rt followed
by washing with DMF (5.times.0.5 mL), methanol (5.times.0.5 mL) and
CH.sub.2Cl.sub.2 (5.times.0.5 mL). The resin was used directly in
the next step.
F.sup.P3: Tagging of E.sup.P3 Using TRITC
TRITC (0.89 mg, 2 .mu.mol) was dissolved in DMF (0.2 mL) and the
solution was added to the resin (E.sup.P3) and left for 2 h at rt
followed by extensive washing DMF (5.times.0.5 mL),
CH.sub.2Cl.sub.2 (5.times.0.5 mL), methanol (5.times.0.5 mL), and
finally water (5.times.0.5 mL) to remove excess dye. The resin was
used directly in the next step.
G.sup.P3: Cleavage of TMR Tagged LacNAc from Support
The resin obtained in the previous experiment F.sup.P3 was covered
with a 1 M solution of LiOH (0.2 mL) and left for 2 h. The liquid
was collected from the beads by suction followed by washing of the
beads with water (3.times.0.5 mL). The collected liquid and
washings were pooled and pH was adjusted to neutral with 10% AcOH.
The dark red solution was adsorbed on a Sep-Pak column (50 mg),
washed with water (2 mL) and eluted with methanol (0.5 mL). The
identity of the product was confirmed by MS (ES) m/z=978 (MH.sup.+)
and the profile was recorded by CE (FIG. 11).
4.2.2 Capture and Processing of Reducing Sugar 5
C.sup.P5: Capture of Lacto-N-tetraose (5) on B.sup.P
A solution was made by dissolving 5 (5.0 mg, 7.1 .mu.mol) in a
mixture of DMSO and AcOH 7:3 (3 mL). This mixture was added to PEGA
resin B.sup.P (175 mg, 35 .mu.mol) and incubated at 60.degree. C.
over night. The resin was washed several times: DMF (5.times.5 mL),
methanol (5.times.5 mL) and used directly in the next
experiments.
D.sup.P5: Capping of C.sup.P5 with Acetic Anhydride
All the resin obtained in experiment C.sup.P5 was treated with a
mixture of Ac.sub.2O and methanol 1:1 (5 mL) for 1 h followed be
washing with DMF (5.times.5 mL), water (2.times.5 mL), methanol
(5.times.5 mL) and used directly in the next experiment.
E.sup.P5: Reduction of D.sup.P5 with BH.sub.3-pyridine
The resin obtained in experiment D.sup.P5 was swelled in methanol
(2 mL) and BH.sub.3-pyridine (200 .mu.L, 8 M in pyridine) was added
followed by addition of 50% CCl.sub.3CO.sub.2H acid in water (400
.mu.L). The reaction was left to proceed for 2 h at rt followed by
washing with DMF (5.times.5 mL), methanol (5.times.5 mL) and
CH.sub.2Cl.sub.2 (5.times.5 mL). Finally the resin was dried down
under vacuum over night and stored at room temperature for further
use.
F.sup.P5: Tagging of E.sup.P5 with Bromine Containing MS-Tag
A small amount of the dried resin E.sup.P5 (10 mg, 0.4 .mu.mol) was
washed with CH.sub.2Cl.sub.2 (3.times.0.5 mL) in order to swell the
resin. A solution was made by dissolving 4-bromophenyl
isothiocyanate (0.85 mg, 4 .mu.mol) in DMF (0.2 mL) and the mixture
was added to the resin and left to react for 2 h at rt followed by
washing of the resin DMF (5.times.0.5 mL), CH.sub.2Cl.sub.2
(5.times.0.5 mL), methanol (5.times.0.5 mL), and finally water
(5.times.0.5 mL). The resin was used directly in the next step.
G.sup.P5: Cleavage of Bromine Tagged Lacto-N-tetraose from
Support
The resin obtained in the previous experiment F.sup.P5 was covered
with a 1 M solution of LiOH (0.2 mL) and left for 2 h. The liquid
was collected from the beads by suction followed by washing of the
beads with water (3.times.0.5 mL). The collected liquid and
washings were pooled and pH was adjusted to slightly acidic (pH
3-4) with 10% AcOH. The solution containing the desired product was
adsorbed on a Sep-Pak column (50 mg), washed with water (2 mL) and
eluted with methanol (0.5 mL). The identity of the product was
confirmed by MS (ES) m/z=1072 (98%, MH.sup.+), 1074 (100%,
MH.sup.+), m/z=1070 (98%, M-H.sup.+), 1072 (100%, M-H.sup.+). FIG.
12 shows the mass-spectrum with an inset expansion where the two
isotopes of bromine can clearly be distinguished.
4.2.3 Capture and Processing of Reducing Sugar Mixture 6
C.sup.P6: Capture of Monosaccharide Mixture 6 (Fuc:Man:GalNac,
2:3:1) on B.sup.P
A series of 3 stock solutions were made by dissolving the 3
individual monosaccharides (Fuc: 16 mg, 0.10 mmol, Man: 18 mg, 0.10
mol, GalNAc: 22 mg, 0.10 mmol) in water (3.times.1.0 mL) and then
diluting the samples 10 times with a mixture of DMSO and AcOH (7:3,
3.times.9 mL) to give 10 mM stock solutions of the 3
monosaccharides. A mixture was now prepared by taking the following
amounts from the 3 stock solutions: Fuc (20 .mu.L, 0.2 .mu.mol),
Man (30 .mu.L, 0.3 .mu.mol) and GalNAc (10 .mu.L, 0.1 .mu.mol).
This monosaccharide solution was diluted further by addition of the
mixture of DMSO and AcOH (7:3, 150 .mu.L) and the whole was added
to PEGA resin B.sup.P (10 mg, 2 .mu.mol) and left to incubate at
60.degree. C. over night. The resin was washed several times: DMF
(5.times.0.5 mL), methanol (5.times.0.5 mL) and used directly in
the next experiments.
D.sup.P6: Capping of C.sup.P6 with Acetic Anhydride
All the resin obtained in experiment C.sup.P6 was treated with a
1:1 mixture of Ac.sub.2O and methanol (0.4 mL) for 1 h followed be
washing with DMF (5.times.0.5 mL), water (2.times.0.5 mL), methanol
(5.times.0.5 mL) and used directly in the next experiment.
E.sup.P6: Reduction of D.sup.P6 with BH.sub.3-pyridine
The resin obtained in experiment D.sup.P6 was covered with methanol
(0.1 mL) and BH.sub.3-pyridine (20 .mu.L, 8 M in pyridine) was
added followed by addition of 50% CCl.sub.3CO.sub.2H in water (40
.mu.L). The reaction was left to proceed for 2 h at rt followed by
washing with DMF (5.times.0.5 mL), methanol (5.times.0.5 mL) and
CH.sub.2Cl.sub.2 (5.times.0.5 mL). The resin was split into 2
separate containers (E.sup.P6.sub.a and E.sup.P6.sub.b, app. 5 mg
each) and used directly in the next steps.
F.sup.P6.sub.a: Tagging of E.sup.P6.sub.a Using TRITC
TRITC (0.5 mg, 1.2 .mu.mol) was dissolved in DMF (0.2 mL) and the
solution was added to the resin (E.sup.P6.sub.a) and left for 2 h
at rt followed by extensive washing DMF (5.times.0.5 mL),
CH.sub.2Cl.sub.2 (5.times.0.5 mL), methanol (5.times.0.5 mL) and
finally water (5.times.0.5 mL) to remove excess dye. The resin was
used directly in the next step.
G.sup.P6.sub.a: Cleavage of TMR Tagged Monosaccharide Mixture from
Support
The resin obtained in the previous experiment (F.sup.P6.sub.a) was
covered with a 1 M solution of LiOH (0.1 mL) and left for 2 h. The
liquid was collected from the beads by suction followed by washing
of the beads with water (3.times.0.5 mL). The collected liquid and
washings were pooled and pH was adjusted to neutral with 10% AcOH.
The dark red solution was adsorbed on a Sep-Pak column (50 mg),
washed with water (2 mL) and eluted with methanol (0.5 mL). The
identity of the 3 tagged products was confirmed by MS (ES) m/z=759
(Fuc, MH.sup.+), 775 (Man, MH.sup.+) 816 (GalNAc, MH.sup.+) and
their profile was recorded by CE (FIG. 13).
F.sup.P6.sub.b: Tagging of E.sup.P6.sub.b with Acetic Anhydride
A 1:1 mixture of Ac.sub.2O and methanol (0.2 mL) was added to the
resin (E.sup.P6.sub.b) and left for 16 h at rt followed by
extensive washing DMF (5.times.0.5 mL), CH.sub.2Cl.sub.2
(5.times.0.5 mL), methanol (5.times.0.5 mL) and finally water
(5.times.0.5 mL). The resin was used directly in the next step.
G.sup.P6.sub.b: Cleavage of Acetic Acid Tagged Monosaccharide
Mixture from Support
The resin obtained in the previous experiment (F.sup.P6.sub.b) was
covered with a 10% solution of NH.sub.4OH (0.1 mL) and left for 2
h. The liquid was collected from the beads by suction followed by
washing of the beads with water (3.times.0.5 mL). The collected
liquid and washings were pooled and evaporate to dryness on a
rotavap, re-dissolved in water (1 mL) and freeze dried. The
identity of the 3 tagged products was confirmed by MS (ES) m/z=356
(Fuc, M-H.sup.+), 372 (Man, M-H.sup.+), 413 (GalNAc, M-H.sup.+).
The ratio of the intensities of the 3 signals was approximately
1.3:2:1.
4.2.4 Capture and Processing of Reducing Sugar Mixture 7
C.sup.P7: Capture of Monosaccharide Mixture 7 (Fuc:Man:GalNac,
1:3:2) on B.sup.P
The same 3 stock solutions of monosaccharides (10 mM each) that
were used in experiment C.sup.P6 was used in the following
experiment. A mixture was prepared by taking the following amounts
from the 3 stock solutions: Fuc (10 .mu.L, 0.1 .mu.mol), Man (30
.mu.L, 0.3 .mu.mol) and GalNAc (20 .mu.L, 0.2 .mu.mol). This
monosaccharide solution was diluted further by addition of the
mixture of DMSO and AcOH (7:3, 150 .mu.L) and the whole was added
to PEGA resin B.sup.P (10 mg, 2 .mu.mol) and left to incubate at
60.degree. C. over night. The resin was washed several times: DMF
(5.times.0.5 mL), methanol (5.times.0.5 mL) and used directly in
the next experiments.
D.sup.P7: Capping of C.sup.P7 with Acetic Anhydride
All the resin obtained in experiment C.sup.P7 was treated with a
1:1 mixture of Ac.sub.2O and methanol (0.4 mL) for 1 h followed by
washing with DMF (5.times.0.5 mL), water (2.times.0.5 mL), methanol
(5.times.0.5 mL) and used directly in the next experiment.
E.sup.P7: Reduction of D.sup.P7 with BH.sub.3-pyridine
The resin obtained in experiment D.sup.P7 was covered with methanol
(0.1 mL) and BH.sub.3-pyridine (20 .mu.L, 8 M in pyridine) was
added followed by addition of 50% CCl.sub.3CO.sub.2H in water (40
.mu.L). The reaction was left to proceed for 2 h at rt followed by
washing with DMF (5.times.0.5 mL), methanol (5.times.0.5 mL) and
CH.sub.2Cl.sub.2 (5.times.0.5 mL). The resin was split into 2
separate containers (E.sup.P7.sub.a and E.sup.P7.sub.b, app. 5 mg
each) and used directly in the next step.
F.sup.P7.sub.a: Tagging of E.sup.P7.sub.a Using TRITC
TRITC (0.5 mg, 1.2 .mu.mol) was dissolved in DMF (0.2 mL) and the
solution was added to the resin (E.sup.P7.sub.a) and left for 2 h
at rt followed by extensive washing DMF (5.times.0.5 mL),
CH.sub.2Cl.sub.2 (5.times.0.5 mL), methanol (5.times.0.5 mL) and
finally water (5.times.0.5 mL) to remove excess dye. The resin was
used directly in the next step.
G.sup.P7.sub.a: Cleavage of TMR Tagged Monosaccharide Mixture from
Support
The resin obtained in the previous experiment (F.sup.P7.sub.a) was
covered with a 1 M solution of LiOH (0.1 mL) and left for 2 h. The
liquid was collected from the beads by suction followed by washing
of the beads with water (3.times.0.5 mL). The collected liquid and
washings were pooled and pH was adjusted to neutral with 10% AcOH.
The dark red solution was adsorbed on a Sep-Pak column (50 mg),
washed with water (2 mL) and eluted with methanol (0.5 mL). The
identity of the 3 tagged products was confirmed by MS (ES) m/z=759
(Fuc, MH.sup.+), 775 (Man, MH.sup.+) 816 (GalNAc, MH.sup.+) and
their profile was recorded by CE (FIG. 14).
F.sup.P7.sub.b: Tagging of E.sup.P7.sub.b with Deuteroacetic
Anhydride
A 1:1 mixture of deuteroacetic anhydride and methanol (0.2 mL) was
added to the resin (E.sup.P7.sub.b) and left for 16 h at rt
followed by extensive washing DMF (5.times.0.5 mL),
CH.sub.2Cl.sub.2 (5.times.0.5 mL), methanol (5.times.0.5 mL) and
finally water (5.times.0.5 mL). The resin was used directly in the
next step.
G.sup.P7.sub.b: Cleavage of Deuterium Tagged Monosaccharide Mixture
from Support
The resin obtained in the previous experiment (F.sup.P7.sub.b) was
covered with a 10% solution of NH.sub.4OH (0.1 mL) and left for 2
h. The liquid was collected from the beads by suction followed by
washing of the beads with water (3.times.0.5 mL). The collected
liquid and washings were pooled and evaporate to dryness on a
rotavap, re-dissolved in water (1 mL) and freeze dried. The
identity of the 3 deuterium tagged products was confirmed by MS
(ES) m/z=359 (Fuc, M-H.sup.+), 375 (Man, M-H.sup.+), 416 (GalNAc,
M-H.sup.+). The ratio of the intensities of the 3 signals was
approximately 1:4:4.
4.2.5 Capture and Processing of Reducing Oligosaccharide Mixture
9
C.sup.P9: Capture of Oligosaccharide Mixture 9 (G2-G7) on
B.sup.P
A solution was made by dissolving an equimolar amount (10 .mu.mol
each) of the pure oligosaccharides G2-G7 in water (1 mL). 100 .mu.L
of the oligosaccharide containing solution was added to a mixture
of DMSO and AcOH (7:3, 0.9 mL) and the whole was added to PEGA
resin B.sup.P (60 mg, 12 .mu.mol) and left to incubate at
50.degree. C. over night. The resin was washed several times: DMF
(5.times.2 mL), methanol (5.times.2 mL) and used directly in the
next experiments.
D.sup.P9: Capping of C.sup.P9 with Acetic Anhydride
All the resin obtained in experiment C.sup.P9 was treated with a
1:1 mixture of Ac.sub.2O and methanol (2 mL) for 1 h followed be
washing with DMF (5.times.2 mL), water (2.times.2 mL), methanol
(5.times.2 mL) and used directly in the next experiment.
E.sup.P9: Reduction of D.sup.P9 with BH.sub.3-pyridine
The resin obtained in experiment D.sup.P9 was covered with methanol
(1 mL) and BH.sub.3-pyridine (150 .mu.L, 8 M in pyridine) was added
followed by addition of 50% CCl.sub.3CO.sub.2H in water (300
.mu.L). The reaction was left to proceed for 2 h at rt followed by
washing with DMF (5.times.2 mL), methanol (5.times.2 mL) and
CH.sub.2Cl.sub.2 (5.times.2 mL). The resin was used directly in the
next step.
F.sup.P9: Tagging of E.sup.P9 Using FITC
FITC (12 mg, 30 .mu.mol) was dissolved in a 1:1 mixture of DMF and
methanol (1 mL) and the solution was added to the resin (E.sup.P9)
and left for 2 h at rt followed by extensive washing DMF (5.times.2
mL), CH.sub.2Cl.sub.2 (5.times.2 mL), methanol (5.times.2 mL) and
finally water (5.times.2 mL) to remove excess dye. The resin was
used directly in the next step.
G.sup.P9: Cleavage of Oligosaccharide Mixture Tagged Using FITC
from Support
The resin obtained in the previous experiment (F.sup.P9) was
covered with a 1 M solution of LiOH (1 mL) and left for 2 h. The
liquid was collected from the beads by suction followed by washing
of the beads with water (3.times.3 mL). The collected liquid and
washings were pooled and pH was adjusted to neutral with 10% AcOH.
The strong yellow solution was adsorbed on a Sep-Pak column (350
mg), washed with water (10 mL) and eluted with methanol (3 mL). The
presence of all 6 tagged oligosaccharides was confirmed by MS (ES)
m/z=881 (G2, MH.sup.+), 1043 (G3, MH.sup.+), 1205 (G4, MH.sup.+),
1367 (G5, MH.sup.+), 1529 (G6, MH.sup.+), 1691 (G7, MH.sup.+) and
the profile of the mixture was recorded by CE (FIG. 15).
4.2.6 Capture and Processing of Oligosaccharides Released from
Ribonuclease B.
C.sup.P10: Capture and Processing of Oligosaccharides from Rnase B
(10) on B.sup.P
Crude oligosaccharides from PNGase F digestion of RNAse B (Sigma,
R-7884) were used after protein removal on a Centricon-10
concentrator (Millipore) followed by carbohydrate purification on a
Carbograph SPE column (150 mg bed weight; Scantec Lab). A solution
was made by dissolving crude oligosaccharides from RNAse B
(10).sup.2 (300 .mu.g, app. 0.2 .mu.mol) in a mixture of DMSO
containing 0.9 M citric acid and THF 2:1 (100 .mu.L). This mixture
was added to PEGA resin B.sup.P (5 mg, 1.0 .mu.mol) and incubated
at 60.degree. C. over night. The resin was washed several times:
DMF (5.times.0.3 mL), methanol (5.times.0.3 mL) and used directly
in the next experiments.
D.sup.P10: Capping of C.sup.P10 with Acetic Anhydride
All the resin obtained in experiment C.sup.P10 was treated with a
1:1 mixture of Ac.sub.2O and methanol (0.2 mL) for 1 h followed be
washing with DMF (5.times.0.3 mL), water (2.times.0.3 mL), methanol
(5.times.0.3 mL) and used directly in the next experiment.
E.sup.P10: Reduction of D.sup.P10 with BH.sub.3-pyridine
The resin obtained in experiment D.sup.P10 was covered with
methanol (0.2 mL) and BH.sub.3-pyridine (10 .mu.L, 8 M in pyridine)
was added followed by addition of 50% CCl.sub.3CO.sub.2H in water
(20 .mu.L). The reaction was left to proceed for 2 h at rt followed
by washing with DMF (5.times.0.3 mL), methanol (5.times.0.3 mL) and
CH.sub.2Cl.sub.2 (5.times.0.3 mL). The resin was used directly in
the next step.
F.sup.P10: Tagging of E.sup.P10 Using FITC
FITC (1.9 mg, 5 .mu.mol) was dissolved in a mixture of DMF and
methanol (1:1, 0.2 mL) and the solution was added to the resin
(E.sup.P10) and left for 2 h at 600 followed by extensive washing
DMF (5.times.0.3 mL), CH.sub.2Cl.sub.2 (5.times.0.3 mL), methanol
(5.times.0.3 mL) and finally water (5.times.0.3 mL) to remove
excess dye. The resin was used directly in the next step.
G.sup.P10: Cleavage of Oligosaccharides from RNAse Tagged Using
FITC from Support
The resin obtained in the previous experiment (F.sup.P10) was
covered with a 1 M solution of LiOH (0.2 mL) and left for 2 h. The
liquid was collected from the beads by suction followed by washing
of the beads with water (3.times.0.5 mL). The collected liquid and
washings were pooled and pH was adjusted to neutral with 10% AcOH.
The yellow solution containing the desired product was adsorbed on
a Sep-Pak column (50 mg), washed with water (2 mL) and eluted with
methanol (0.5 mL). The profile of the labelled oligosaccharides was
analysed by CE. The CE (FIG. 16) indicates the presence of several
oligosaccharides and some unidentified contaminants. The identity
of at least one of the known components was confirmed by MS (ES)
m/z 1775 (Man.sub.5GlcNAcGlcNAcCH.sub.2--N--(R)-TAG, MH.sup.+).
4.3 Capture and Processing of Representative Reducing Sugars on CPG
Supports.
4.3.1 Capture and Processing of 2 on B.sup.1
C.sup.12: Capture of galactose (2) on B.sup.1
B.sup.1 (20 mg, 0.6 .mu.mol) was treated with 2 (6.6 .mu.L, 1 mg/mL
water, 0.03 .mu.mol) in citrate-phosphate buffer (113 .mu.L) and
left over night at 55.degree. C. The beads were transferred to a
syringe and washed with water (3.times.0.5 mL) and ethanol
(3.times.0.5 mL) giving C.sup.12.
D.sup.12: Capping of C.sup.12 with Acetic Anhydride
C.sup.12 (0.6 .mu.mol) were capped with 50% Ac.sub.2O in ethanol
for 15 min at rt and washed with ethanol (3.times.0.5 mL) giving
D.sup.12.
E.sup.12: Reduction of D.sup.12 with BH.sub.3-pyridine
D.sup.12 (0.6 .mu.mol) was treated with 100 .mu.L of a solution of
BH.sub.3-pyridine (25 .mu.L), 50% CCl.sub.3CO.sub.2H (50 .mu.L) in
ethanol (500 .mu.L). The mixture was left for 2 h at rt. The beads
were washed with ethanol (3.times.0.5 mL) giving E.sup.12.
F.sup.12: Labelling of E.sup.12 with TRITC
E.sup.12 (0.6 .mu.mol) was treated with TRITC (100 .mu.L of 1.0 mg
in 300 .mu.L NMP and 300 .mu.L CH.sub.2Cl.sub.2) and left for 2 h
at rt. The beads were washed with CH.sub.2Cl.sub.2 (3.times.0.5
mL), ethanol (3.times.0.5 mL), and water (3.times.0.5 mL) giving
F.sup.12 (red beads).
G.sup.12: Base Treatment of F.sup.12
F.sup.12' (0.6 .mu.mol) was treated with 1 M solution of LiOH (100
.mu.L) for 1 h at rt and the red solution was isolated and
neutralised with 50% AcOH in water giving G.sup.12 (red solution)
which were passed through a Sep-Pak column (30% CH.sub.3CN in
water) and analysed by MS (775.3, MH.sup.+) and CE (FIG. 17).
4.3.2 Capture and Processing of 5 on B.sup.1
C.sup.15: Capture of LNT (5) on B.sup.1
B.sup.1 (20 mg, 0.6 .mu.mol) was treated with 5 (25 .mu.L, 2 mg/mL
water, 0.03 .mu.mol) in citrate-phosphate buffer (113 .mu.L) and
left over night at 55.degree. C. The beads were transferred to a
syringe and washed with water (3.times.0.5 mL) and ethanol
(3.times.0.5 mL) giving C.sup.15.
D.sup.15: Capping of C.sup.15 with Acetic Anhydride
C.sup.15 (0.6 .mu.mol) was treated with 50% Ac.sub.2O in ethanol
for 15 min at rt and washed with (3.times.0.5 mL) giving
D.sup.15.
E.sup.15: Reduction of D.sup.15 with BH.sub.3-pyridine
D.sup.15 (0.6 .mu.mol) was treated with 100 .mu.L of a solution of
BH.sub.3-pyridine (25 .mu.L), 50% CCl.sub.3CO.sub.2H (50 .mu.L) in
ethanol (500 .mu.L). The mixture was left for 2 h at rt. The beads
were washed with ethanol (3.times.0.5 mL) giving E.sup.15.
F.sup.15: Labelling of E.sup.15 with TRITC
E.sup.15 (0.6 .mu.mol) was treated with TRITC (100 .mu.L of 1.0 mg
in 300 .mu.L NMP and 300 .mu.L CH.sub.2Cl.sub.2) and left for 2 h
at rt. The beads were washed with CH.sub.2Cl.sub.2 (3.times.0.5
mL), ethanol (3.times.0.5 mL), and water (3.times.0.5 mL) giving
F.sup.15 (red beads).
G.sup.15: Base Treatment of F.sup.15
The resin was treated with a 1 M solution of LiOH (100 .mu.L) for 1
h at rt and the red solution was isolated by filtration and the
beads were washed with water (3.times.75 .mu.L) and neutralised
with 50% AcOH in water giving G.sup.15 (red solution) which were
passed through a Sep-Pak column (30% CH.sub.3CN in water) and
analysed by MS (ES) m/z=1300.6 (M-H.sup.+), 1302.4 (MH.sup.+) and
by CE (FIG. 18).
Alternatively, E.sup.15 could be labelled with
1-fluoro-2,4-dinitrobenzene (Sanger's reagent, (FIG. 8) as follows.
The resin was treated with Sanger's reagent (20 eq, 0.4 .mu.L,
Sigma) and TEA (10 eq, 0.2 .mu.L) in ethanol (70 .mu.L) for 2 h at
55.degree. C. The beads were washed with ethanol (3.times.0.5 mL),
CH.sub.2Cl.sub.2 (3.times.0.5 mL), ethanol (3.times.0.5 mL), and
water (3.times.0.5 mL) (yellow beads), then treated with 1 M
solution of LiOH (70 .mu.L) for 1 h at rt (brown solution). The
solution was collected by filtration and the beads were washed with
water (3.times.50 .mu.L). The mixture was neutralised with 50% AcOH
(yellow solution). The mixture was passed through a Sep-Pak column
with 30% CH.sub.3CN in water. MS (ES) m/z=1023.1 (M-H.sup.+).
4.3.3 Capture and Processing of Mixture 8 on B.sup.1
C.sup.18: Capture of Galactose (2) and LNT (5) on B.sup.1
B.sup.1 (20 mg, 0.6 .mu.mol) was treated with 2 (6.6 .mu.L, 1 mg/mL
water, 0.03 .mu.mol), 5 (25 .mu.L, 2 mg/mL water, 0.03 .mu.mol),
citrate-phosphate buffer (100 .mu.L), and left over night at
55.degree. C. The beads were washed with water (3.times.0.5 mL) and
ethanol (3.times.0.5 mL) giving C.sup.18.
D.sup.18: Capping of C.sup.18 with Acetic Anhydride
The remaining hydroxylamines in C.sup.18 (0.6 .mu.mol) were capped
with 50% Ac.sub.2O in ethanol for 15 min at rt and washed with
ethanol (3.times.0.5 mL) giving D.sup.18.
E.sup.18: Reduction of D.sup.18 with BH.sub.3-pyridine
D.sup.18 (0.6 .mu.mol) was treated with 100 .mu.L of a solution of
BH.sub.3-pyridine (Fluka, 25 .mu.L), 50% CCl.sub.3CO.sub.2H (50
.mu.L) in ethanol (500 .mu.L). The mixture was left for 2 h at rt.
The beads were washed with ethanol (3.times.0.5 mL) giving
E.sup.18.
F.sup.18: Labelling of E.sup.18 Using TRITC
E.sup.18 (0.6 .mu.mol) was treated with TRITC (100 .mu.L of 1.0 mg
in 300 .mu.L NMP and 300 .mu.L CH.sub.2Cl.sub.2) and left for 2 h
at rt giving F.sup.18. The beads were washed with CH.sub.2Cl.sub.2
(3.times.0.5 mL), ethanol (3.times.0.5 mL), and water (3.times.0.5
mL) (red beads).
G.sup.18: Base Treatment of F.sup.18
F.sup.18 was treated with 1 M solution of LiOH (100 .mu.L) for 1 h
at rt and the red solution was isolated and neutralised with 50%
AcOH in water giving G.sup.18 (red solution) which were passed
through a Sep-Pak column (30% CH.sub.3CN in water) and analysed by
CE (FIG. 19).
5. Reaction of Immobilized Oligosaccharides with Enzymes
5.1 Reaction of an Immobilized Tagged Oligosaccharide with a
Glycosidase
5.1.1 Reaction of immobilized lacto-N-tetraose (LNT, 5) of
structure F (cap=acetyl, TAG=TMR) with beta-galactosidase (bovine
testes, SIGMA product G-4142, 1 U/mL) on CPG supports with none
(F.sup.05), one (F.sup.15) and two (F.sup.25) spacers. All 3
immobilized oligosaccharides were prepared essentially as described
for F.sup.15 (section 4.3.2).
The solid supports (5 mg) were incubated with beta-galactosidase
(100 .mu.L of 0.2 U/mL solution in 0.1 M citrate/phosphate buffer
pH 5.0 containing 0.2% BSA for 23 h at 37.degree. C., and the resin
was then washed with 3.times. water, 3.times. ethanol, 3.times.
CH.sub.2Cl.sub.2, 3.times. Et ethanol OH, and 3.times. water. The
beads were treated with 1 M solution of LiOH (60 .mu.L) for 1 h at
rt giving products of the general structures G).sub.5, G.sup.15,
and G.sup.25 in solution. Each red solution was collected by
filtration. The filtrate was neutralised with 50% AcOH and analysed
using CE.
FIG. 20 shows that there was no detectable cleavage of galactose
from LNT for F.sup.05, 39% conversion for F.sup.15 (i.e. 39% of the
tetrasaccharide had lost the terminal Gal residue and been
converted to the trisaccharide) and 83% conversion for F.sup.25.
The nature of the spacer was therefore found to be important to the
course of the enzyme reaction.
5.1.2 Reaction of immobilized maltotriose F.sup.24 (cap=acetyl,
TAG=TMR) with glucoamylase 2 from Aspergillus niger (kindly
provided by Dr. Birte Svensson, Carlsberg Laboratories) on CPG
support with two spacers. F.sup.24 was prepared essentially as
described for F.sup.15 (section 4.3.2) but using maltotriose (G3,
FIG. 2) as the reducing sugar and B.sup.2 as the solid support.
F.sup.24 (ca 5 mg) was incubated for 23 h at 37.degree. C. with 50
.mu.L of 0.1 mg/mL of enzyme in 0.1 M sodium acetate buffer pH 5.5
containing 0.2% BSA. After washing and cleavage as described above,
the product was analyzed by CE (FIG. 21), which showed complete
conversion of immobilized labelled maltotriose to a new peak
eluting between labelled maltotriose and glucose, therefore
assigned as the maltobiose (G2) TMR adduct.
5.2 Reaction of an immobilized untagged oligosaccharide with a
glycosidase and capture of the released reducing monosaccharide on
the same support.
Reaction of immobilized LNT of structure C.sup.25 (non-reduced,
non-capped, non-tagged) with beta-galactosidase (bovine testes) was
carried out on CPG solid support with two spacers. C.sup.25 was
prepared essentially as described for C.sup.15 (section 4.3.2).
Prior to use, the enzyme solution was freed from small-molecule
contaminants by repeated centrifugation using a Microcon YM-3
centrifugal filter device (Millipore). C.sup.25 (5 mg) was
incubated for 23 h at 37.degree. C. with 55 .mu.L of 0.9 U/mL of
enzyme in 0.1 M citrate/phosphate, pH 5.0, containing 0.2% BSA, and
then a further 20 h at 55.degree. C. to permit capture of released
galactose. The solid was washed, reduced, capped with acetic
anhydride, tagged using TRITC and cleaved with LiOH as described
above for the conversion of C.sup.15 to G.sup.15. The CE of cleaved
product is shown in FIG. 22 which shows the presence of unreacted
LNT (32%) and similar amounts of both the TMR-labelled product
trisaccharide and cleaved galactose. This experiments confirms the
capture of cleaved sugar on the same uncapped support from which it
was cleaved.
6. Variation of Capping Agents
6.1. Capping of C to Produce D
A selection of capping agents was used to effect the conversions C
goes to D (FIG. 1). C.sup.22 was used as the substrate (where the
solid was CPG with 2 spacers and the captured sugar was galactose).
The amino groups on C were then capped with, among others, acetic
anhydride, benzoic anhydride, tricholoracetic anhydride and
dibromoxylene (FIG. 6). The capping was carried with 50% solutions
of the capping agent in ethanol, for 15-120 min at rt. The samples
were then processed as described for the conversion of C.sup.12 to
G.sup.12 (section 4.3.1), i.e., reduction, labelling using TRITC,
base-cleavage and analysis by CE. The results are shown in FIG. 23
which shows that all conditions provided the target TMR-labelled
galactose (compound 21, FIG. 5) with varying amounts of other
impurities appearing before compound 21 in the
electropherogram.
6.2 Example of Capping of C.sub.red to Produce E
C.sup.22 from section 6.1 above was reduced with BH.sub.3-pyridine
as described for the conversion of D.sup.12 to E.sup.12 above
(section 4.3.1). The product C.sub.red.sup.22 differs from E.sup.12
in that it contains uncapped NH.sub.2 groups. C.sub.red.sup.22 (5
mg) was reacted with benzoic acid NHS-ester (0.4 mg, 1.75 .mu.mol)
and TEA (1.0 .mu.L) in DMF (50 .mu.L) over night at 60.degree. C.
The product of the reaction having the general structure E.sup.22
(with the cap being a benzoate) was then washed and processed as
usual, by tagging using TRITC, cleavage and analysis by CE. FIG. 24
shows the product to be substantially the same as that formed by
the sequence C goes to D goes to E and on to G. The identity of the
product was confirmed by its MS (ES) m/z=775.0 (MH.sup.+).
7. Example of the Use of a Tether
E Goes to H Goes to I Goes to J (FIG. 1)
Synthesis of 29 as Example of X-Tether-Y.sub.p
29: 4-Isothiocyanato-benzyl)-carbamic acid 9H-fluoren-9-ylmethyl
ester
To a solution of 4-aminobenzylamine (0.93 mL, 8.20 mmol) in
anhydrous CH.sub.2Cl.sub.2 (20 mL) was added TEA (1.15 mL, 8.27
mmol) followed by a solution of Fmoc-N-hydroxysuccinimide ester
(2.48 g, 7.35 mmol) in dry CH.sub.2Cl.sub.2 (10 mL). After 30 min
of stirring, CH.sub.2Cl.sub.2 (100 mL) was added and the mixture
was washed successively with sat. aq. NaHCO.sub.3 (2.times.50 mL)
and brine (50 mL), and dried (Na.sub.2SO.sub.4). The solvent was
removed under reduced pressure and the residue purified by dry
column vacuum chromatography (0-60% EtOAc in n-heptane) to yield
the Fmoc-protected material (4-Amino-benzyl)-carbamic acid
9H-fluoren-9-ylmethyl ester (2.30 g, 91%). .sup.1H-NMR (250 MHz,
DMSO-d6) =4.03 (2H, d, J=5, 3 Hz), 4.22 (1H, t, J=6, 8 Hz), 4.33
(2H, d, J=6, 8 Hz), 4.95 (2H, s), 6.53 (2H, d, J=8.3 Hz), 6.92 (2H,
d, J=8.2 Hz), 7.29-7.44 (4H, m), 7.64-7.72 (3H, m), 7.88 (2H, d,
J=7.3 Hz). .sup.13C-NMR (63 MHz, DMSO-d6) 43.97, 47.19, 65.65,
114.09, 120.46, 121.75, 125.58, 127.11, 127.42, 127.96, 128.47,
129.30, 141.13, 144.32, 147.89, 156.63. MS (ES) m/z=345
(MH.sup.+).
A solution of (4-Amino-benzyl)-carbamic acid 9H-fluoren-9-ylmethyl
ester (718 mg, 2.09 mmol) in CH.sub.2Cl.sub.2 (30 mL) was added
dropwise to a solution of thiophosgene (199 .mu.L, 2.61 mmol) in a
CH.sub.2Cl.sub.2-water mixture (40 mL, 1:1, v/v). After the mixture
was stirred over night, the organic phase was isolated and dried
(Na.sub.2SO.sub.4). The solvent was removed under reduced pressure
and the residue purified by dry column vacuum chromatography
(0-100% CH.sub.2Cl.sub.2 in n-heptane) to yield 29 (643 mg, 80%).
.sup.1H-NMR (250 MHz, DMSO-d6) =4.18-4.25 (3H, m), 4.38 (2H, d,
J=6.7 Hz), 7.25-7.45 (8H, m), 7.69 (2H, d, J=7.3 Hz), 7.87-7.90
(3H, m). .sup.13C-NMR (63 MHz, DMSO-d6) =43.64, 47.19, 65.70,
115.55, 120.48, 125.15, 125.49, 126.20, 127.42, 127.98, 128.72,
128.83, 133.55, 136.29, 140.26, 141.16, 144.23, 156.74. MS (ES)
m/z=387 (MH.sup.+).
H.sup.P5: Attachment of Fmoc-Protected Amino Tether to E.sup.P5
Using 29 (FIG. 9)
5 mg of the dried resin (E.sup.P5) (0.2 .mu.mol) was washed a
couple of times with CH.sub.2Cl.sub.2 to ensure proper swelling of
the resin. The Fmoc-protected tether (29) (0.8 mg, 2 .mu.mol) was
dissolved in DMF (0.2 mL) and added to the resin and left to react
for 2 h. The resin was washed with DMF (5.times.0.5 mL),
CH.sub.2Cl.sub.2 (5.times.0.5 mL) and the Fmoc protecting group was
removed under standard conditions (20% piperidine in DMF, 0.5 ml
2.times.10 min). The resin was used directly in the next experiment
after washing with DMF (5.times.0.5 mL)
I.sup.P5: Tagging of H.sup.P5 Using TRITC
The resin obtained in experiment H.sup.P5, now containing a free
primary amino group, was incubated with TRITC (0.9 mg, 2 .mu.mol)
in DMF (0.2 mL) at rt for 2 h followed by extensive washing with
DMF (5.times.0.5 mL), CH.sub.2Cl.sub.2 (5.times.0.5 mL), methanol
(5.times.0.5 mL) and finally water (5.times.0.5 mL) to remove
excess dye. The resin was used directly in the next step.
J.sup.P5: Cleavage of Lacto-N-Tetraose Tagged Using TRITC Via an
Amino Tether
The resin obtained in the previous experiment (I.sup.P5) was
covered with a 1 M solution of LiOH (0.2 mL) and left for 2 h. The
liquid was collected from the beads by suction followed by washing
of the beads with water (3.times.0.5 mL). The collected liquid and
washings were pooled and pH was adjusted to slightly acidic (pH
3-4) with 10% AcOH. The dark red solution containing the desired
product was adsorbed on a Sep-Pak column (50 mg), washed with water
(2 mL) and eluted with methanol (0.5 mL). The identity of the
product was confirmed by MS (ES) m/z=1465 (MH.sup.+).
Capillary Electrophoresis Analysis of Labeled Carbohydrates
Capillary electrophoresis (CE) was performed using an automated
PrinCE 2-lift, model 560 CE system (Prince Technologies, The
Netherlands). Separations were carried out in an uncoated
fused-silica capillary of 75 .mu.m ID with an effective length in
the range 50-75 cm (plus 30 cm of extra length from the detection
window to the outlet), thermostatically controlled at 25.degree. C.
The CE background electrolyte (BGE) was either (A) 50 mM borate
buffer pH 9.3 containing 150 mM SDS or (B) 0.2 M borate buffer pH
9.3 containing 0.8% (w/v) .gamma.-CD (Sigma, C-4892). Conditions A
were used for the analyses shown in FIGS. 11 and 15-22. Conditions
B were used for the analyses shown in FIGS. 10, 13, 14, 23 and
24.
The capillary was conditioned at room temperature by rinsing at
2000 mbar for 30 min with 1 M NaOH, 10 min with water, and 10 min
with BGE before use. Between runs the capillary was washed at 2000
mbar for 3 min with 1 M NaOH, 3 min with water, and 3 min with BGE.
Samples were injected hydrodynamically for 6 sec at 50 mbar and
electrophoresed across a potential difference of 25 kV. All
experiments were carried out at a normal polarity, i.e. inlet
anodic. Detection was carried out using a fluorescence detector
(Argos 250B, Flux Instruments, Switzerland) equipped with the
appropriate filters. For samples labeled using TRITC, the
excitation and emission filters were respectively 546.1/10 and 570
nm. For samples labeled using FITC, the excitation and emission
filters were respectively UG11 (200-400 nm) and 495 nm.
ABBREVIATIONS
The following abbreviations have been used throughout the present
application: AMP CPG Aminopropyl controlled pore glass BGE
Background electrolyte BSA Bovine serum albumin CE Capillary
electrophoresis CPG Controlled pore glass DIPEA
N,N-Diisopropylethylamine DMF N,N-Dimethylformamide ES Electrospray
FITC Fluorescein isothiocyanate Fmoc 9-Fluorenylmethyloxycarbonyl
HRMS High resolution mass spectroscopy LNT Lacto-N-tetraose MS Mass
spectroscopy NHS N-Hydroxysuccinimide NMP 1-methyl-2-pyrrolidone
PEGA Polyethylenglycol acrylamide polymer RNAse B Ribonuclease B rt
Room temperature TBTU
N,N,N',N'-tetramethyl-O-(1H-benzotriazol-1-yl)uroniumtetrafluorborate
TEA Triethylamine TMR Tetramethylrhodamine TRITC
Tetramethylrhodamine isothiocyanate
* * * * *